> ## Documentation Index
> Fetch the complete documentation index at: https://aipro.placetel.de/docs/llms.txt
> Use this file to discover all available pages before exploring further.
# Prompting Guide
> A guide to writing effective AI instructions: recommended structure, tips & tricks, examples, tools, and variables.
The **AI instruction (prompt)** is the central control element of your voice agent. It defines who the agent is, how it speaks, what it should achieve, and what it must never do.
Instructions for voice agents differ significantly from prompts for chat applications, because they have to meet two requirements at the same time:
1. **Sound natural.** Text that looks good in writing quickly sounds stiff and robotic when read aloud. The instruction must actively work against the language model's tendency toward perfect written prose.
2. **Work reliably.** The agent must call tools correctly, follow rules, hand over to humans, and deal with errors - live on the phone, with no user interface as a fallback.
An instruction optimized only for naturalness produces a charming agent that makes things up. A purely rule-based instruction produces a reliable agent that sounds like a recorded announcement. Good prompts achieve both - this guide shows how.
## Recommended structure
Organize your instruction into named sections with Markdown headings. This prevents rules from different contexts from blending together, and language models pay particularly reliable attention to certain headings - especially `# Guardrails`.
Use **English section headings with German content**. This is the established convention, and models respond most reliably to the English headings. All the text under the headings stays German.
The proven order:
```markdown theme={null}
# Personality → Who is the agent?
# Environment → Where is it, who is it talking to?
# Tone → How does it speak? How long are the answers?
# Goal → What should it achieve? (numbered steps)
# Guardrails → What must it never do?
# Tools → When and how does it use which tool?
# Error handling → What does it do when something fails?
```
Not every instruction needs all sections - a pure FAQ agent without tools can omit `# Tools` and `# Error handling`. The **order**, however, should be preserved: persona before behavior, behavior before rules, rules before tool usage.
### # Personality
Defines who the agent is. Describe the personality as **audible behavior**, not as adjectives - "friendly and helpful" is the default mode of every language model anyway and changes nothing.
```markdown theme={null}
# Personality
Du bist Lena, die telefonische Assistentin der Autowerkstatt Meier.
Du klingst ruhig und souverän, ohne übertrieben begeistert zu wirken.
Du fängst Sätze auch mal mit "Also", "Ja" oder "Okay" an.
Wenn du etwas nicht weißt, sagst du das offen - du erfindest nichts.
```
### # Environment
Tells the agent where it is and what it can assume about the callers. A short but effective section: a frustrated caller needs a different opening than a curious prospect.
```markdown theme={null}
# Environment
Du führst ein Telefongespräch. Die Anrufer sind Kunden der Werkstatt und
möchten meist einen Termin vereinbaren oder haben eine Frage zu einer
laufenden Reparatur. Manche Anrufer sind in Eile.
```
### # Tone
Sets response length, pace, and speaking style. Every voice instruction should contain a **concrete target length** - this is one of the most effective single sentences in the entire prompt.
```markdown theme={null}
# Tone
Antworte in 1–2 kurzen Sätzen, außer der Anrufer bittet um Details.
Nutze kurze Bestätigungen zwischendurch: "Alles klar", "Einen Moment", "Verstehe".
Passe dich dem Tempo des Anrufers an - knapp, wenn er knapp ist.
```
### # Goal
Numbered steps the agent should work through. For transactional agents (appointment booking, order status) this is the most important section: it turns vague expectations into an unambiguous flow.
```markdown theme={null}
# Goal
Führe die Terminvereinbarung in dieser Reihenfolge durch:
1. Kläre das Anliegen (Inspektion, Reifenwechsel, Reparatur).
2. Frage nach dem Wunschtermin. Ist er nicht frei, schlage direkt
konkrete Alternativen vor.
3. Erfasse Vor- und Nachnamen. Bestätige bei seltenen Namen die Schreibweise.
4. Buche den Termin und wiederhole Datum und Uhrzeit zur Bestätigung.
```
### # Guardrails
Non-negotiable rules. Phrase guardrails as "never" statements and collect them centrally here instead of scattering them across the instruction.
```markdown theme={null}
# Guardrails
Nenne niemals Preise oder Zusagen, die nicht in deinen Informationen stehen.
Gib niemals Daten anderer Kunden weiter.
Wenn du eine Antwort nicht weißt, sage das offen und biete an
weiterzuverbinden. Erfinde nichts. Das ist wichtig.
```
### # Tools
One subsection per tool with three blocks: **when** it is used, **how** it is used, and **what happens on errors**. Details in the section [Tools in the instruction](#tools-in-the-instruction).
### # Error handling
Overarching rules for the case that a tool fails or returns unexpected data.
```markdown theme={null}
# Error handling
Wenn ein Tool-Aufruf fehlschlägt:
1. Sag es ehrlich: "Da klemmt gerade etwas bei mir im System."
2. Erfinde keine Informationen. Das ist wichtig.
3. Versuche es einmal erneut. Klappt es wieder nicht, biete einen
Rückruf oder die Weiterleitung an einen Mitarbeiter an.
```
## Tips & tricks
### Show, don't describe
Vague style instructions ("be casual", "sound natural") accomplish almost nothing. The most effective thing you can do: write **concrete example utterances** into the instruction - each as a pair of the robotic default version and the desired natural version.
```markdown theme={null}
SO KLINGEN GUTE ANTWORTEN:
Statt: "Selbstverständlich kann ich Ihnen dabei behilflich sein."
Besser: "Ja, klar - das mach ich gerne für Sie."
Statt: "Einen Moment bitte, ich rufe Ihre Daten auf."
Besser: "Okay, einen Moment - ich schau da eben für Sie nach."
Statt: "Leider kann ich Ihre Bestellung nicht finden."
Besser: "Hmm, ich finde die gerade nicht - können Sie mir die Nummer
nochmal durchgeben?"
Statt: "Ist sonst noch etwas, womit ich Ihnen helfen kann?"
Besser: "Gibt's sonst noch was, wo ich helfen kann?"
```
Four to eight such pairs are enough. Cover the most common situations: confirming, looking something up, not knowing something, saying goodbye. The model learns considerably better from examples than from adjectives.
### Anchor important rules twice
Language models weight the most recent conversation turns more heavily than instructions far back in the context. Your 1–2 most important rules therefore belong **in two places**: once in `# Guardrails`, once in the section where they concretely apply (e.g. at the respective tool). Append **"Das ist wichtig."** ("This is important.") to truly critical sentences - used sparingly, this works reliably.
The one rule that belongs in **every** instruction with tools, twice:
> Wenn du etwas nicht weißt oder ein Tool fehlschlägt, sage das offen. Erfinde niemals Informationen. Das ist wichtig.
Otherwise the model's instinct to be "helpful" produces invented appointment confirmations, prices, or order statuses - the most expensive mistakes in live operation.
### Formal or informal address - decide and stick to it
Decide whether the agent addresses callers with the formal **Sie** or the informal **Du**, and keep this consistent in **every** example, every phrase, and every error message. A mix immediately sounds jarring on the phone. Follow the way your brand addresses customers elsewhere.
### Keep it lean
Every line must earn its place. Long instructions slow down response time - and on the phone, every delay is directly noticeable.
### Instruct, don't motivate
"Try really hard to be especially friendly!" wastes tokens. Write **what** the agent should do. And use ALL CAPS and "NIEMALS" (never) sparingly - if everything is emphasized, nothing is.
## Nuances: spoken language on the phone
Callers speak their details out loud - the model has to convert them into written form before passing them to a tool. This is where most errors happen in live operation. Write the conversion rules directly into the instruction or into the tool description.
### Times: the "halb drei" trap
The most common reliability error with German-language voice agents: **"halb drei" means 14:30 (2:30 PM), not 15:30.** Don't rely on the model getting this right - write the rule into the instruction with examples:
| Spoken (German) | Means |
| ----------------------------------------------------- | ----- |
| "halb drei" | 14:30 |
| "Viertel vor drei" | 14:45 |
| "Viertel nach drei" | 15:15 |
| "drei Uhr" | 15:00 |
| "Viertel drei" *(regional, southern Germany/Austria)* | 14:15 |
| "drei viertel drei" *(regional)* | 14:45 |
### Dates, phone numbers, numbers
* **Dates:** The format is DD.MM.YYYY - "der dritte Mai" (the third of May) becomes `03.05.`, not `05/03`. The agent can only resolve relative expressions like "übermorgen" (the day after tomorrow) if it knows the current date - use the [date variables](#variables-in-the-instruction) for this.
* **Phone numbers:** German callers often dictate in groups of two ("dreißig vierundsiebzig" = 30 74). Rule for the instruction: resolve digit pairs, remove separators, replace a leading 0 with +49 where needed.
* **Numbers:** The decimal separator is the comma (`1,50 €`), the thousands separator is the period (`1.500`). "Einundzwanzig" (one-and-twenty) is 21 - the model has to reverse the order.
### Avoid email addresses on the phone
Avoid collecting email addresses in the voice channel where possible. Capturing them error-free over the phone is difficult in practice (special characters, spellings, domains) and frequently leads to misdelivered confirmations. An **SMS to the calling number** is usually the more reliable route.
If it has to be done: callers say "ät" or "Klammeraffe" for `@`, "Punkt" for `.`, "Bindestrich" for `-`, and spell out following the pattern "M wie Martha". Write this conversion into the tool description - and have the agent read the address back for confirmation.
### When in doubt: read it back
The most effective single line for any agent that processes bookings or data:
```markdown theme={null}
Wenn du dir bei einer Angabe nicht sicher bist - Datum, Uhrzeit, Name,
Telefonnummer - lies sie einmal zurück und lass sie dir bestätigen,
bevor du sie weiterverwendest. Das ist wichtig.
```
## ElevenLabs v3 prompting
If your agent uses an **ElevenLabs v3 voice**, a few additional rules apply to speech output. v3 reads **audio tags** in square brackets as stage directions for delivery, and it reacts much more strongly to punctuation than older voices. Both can be used deliberately in the instruction - and both can quickly make an agent sound over-acted. This section describes what belongs in the instruction so that speech output stays natural and reliability does not suffer.
Audio tags only take effect in the **Standard Conversation** type (STT → LLM → TTS), where the language model's responses are passed to speech output as text. You choose the voice and its settings in the agent's [voice and audio settings](/docs/en/conversation-audio).
### Audio tags
Audio tags are words in square brackets that v3 does not read aloud but interprets as an instruction for delivery - for example `[whispering]`, `[sighs]`, `[laughs]`, `[pauses]`, or `[rushed]`. They control **how** something is said, not **what** is said.
In the voice agent, the language model writes the tags into its responses itself. The instruction therefore defines which tags the agent may use, how often, and when. Without this guidance, the model either uses no tags at all or scatters them uncontrolled.
Two ground rules:
* **Audible delivery only.** A tag describes something that can be heard on the phone: pace, volume, tone, a pause, a sigh. Tags for visible things like `[standing]` or `[grinning]` have no audible counterpart, and sound effects like `[music]` or `[applause]` do not belong in a customer conversation.
* **Tags never change the message.** A tag must not add content, invent anything, or soften a rule from `# Guardrails`. And it must never end up in a tool parameter - a `[pauses]` in the name field of an appointment booking is a data error.
### Pauses
In v3, pauses come from the text itself:
| Means | Effect |
| ------------------- | ---------------------------------------------------- |
| Ellipsis `...` | A pause with weight - "One moment... let me check." |
| Period, comma, dash | Normal speech rhythm, a short breath |
| `[pauses]` | A deliberate, noticeable pause at exactly this point |
For most customer conversations, punctuation is entirely sufficient. `[pauses]` is the exception for moments where the pause itself makes a statement - for instance before the agent delivers bad news.
### Use sparingly
One tag per response is a lot; most responses need none. And a tag has to fit the selected voice and the situation: a calm support voice should not be `[shouting]` or `[laughs harder]`, and a serious, professional voice often reacts unnaturally to playful tags. The voice needs to be similar to the desired delivery in the first place - a tag amplifies what is already in the voice, it does not create it.
For customer-service agents, a short **allow-list** has proven effective: three or four restrained tags, named explicitly - everything else is off-limits. Use the English tag names from the ElevenLabs documentation, even in German instructions; this matches the "English headings, German content" convention.
### Punctuation and capitalization
v3 reads punctuation as a delivery instruction: ellipses slow down and add weight, CAPITAL LETTERS are emphasized, regular punctuation sets the rhythm. The consequence for the instruction: the model copies the example utterances from the prompt (the "Statt/Besser" pairs) - including their punctuation. Write them the way they should sound.
Do not rely on assumptions for any of these effects. How strongly a voice reacts to a tag or a punctuation mark differs from voice to voice - test every phrasing with the voice you actually selected.
### Examples
A `# Tone` section that releases audio tags in a controlled way:
```markdown theme={null}
# Tone
Answer in 1–2 short sentences unless the caller asks for details.
You speak through an ElevenLabs v3 voice. You may use audio tags in
square brackets to control your delivery - at most one tag per
response, and only where it audibly fits the situation.
Allowed: [pauses], [quietly], [curious]
Not allowed: [shouting], [laughs], [excited], [sighs], sound effects
Make pauses with punctuation: "One moment... let me check."
```
Appropriate versus over-acted use side by side - the pairs work directly as example utterances in the prompt:
```markdown theme={null}
THIS IS WHAT GOOD v3 RESPONSES SOUND LIKE:
Good: "Okay, one moment... let me check the calendar."
Overdone: "[excited] Okay! [pauses] One moment, [whispering] let me
check the calendar!"
Good: "Hmm... that slot is already taken - but I still have Thursday
at ten."
Overdone: "[frustrated] [sighs] That slot is already taken."
Good: "[curious] And which vehicle is this about?"
Overdone: "[curious] [excited] And [pauses] which vehicle [laughs] is
this about?"
```
The rule that additionally belongs in `# Guardrails` for v3 voices:
```markdown theme={null}
Audio tags only change how you speak - never what you say.
Never write an audio tag into a tool parameter (name, date, time,
phone number). This is important.
```
**Test v3 with the voice you actually selected.** How a voice reacts to tags and punctuation depends on the voice itself - cloned and designed voices often behave differently from library voices, and a high stability setting dampens the effect of tags. Check every allowed tag in the browser test with exactly this voice. If the voice reacts unnaturally, remove the tag from the allow-list instead of rescuing the phrasing.
Further reading at ElevenLabs: [Audio tags and situational awareness in Eleven v3](https://elevenlabs.io/blog/eleven-v3-situational-awareness) and [Prompting Eleven v3](https://elevenlabs.io/docs/overview/capabilities/text-to-speech/best-practices#prompting-eleven-v3) in the text-to-speech best practices.
## Tools in the instruction
[Tools](/docs/en/tools) (appointment booking, SMS, email, API requests, n8n) are created in the sidebar and activated per agent in the Voice Wizard. The **condition** on the tool controls when it is fundamentally available - the **instruction** describes how it fits into the conversation flow.
Describe each tool in the instruction with three blocks:
```markdown theme={null}
# Tools
## Terminbuchung
Wann: Erst wenn Anliegen, Wunschtermin und Name vollständig vorliegen.
Wie:
1. Lies dem Anrufer Datum und Uhrzeit zur Bestätigung vor.
2. Buche erst nach ausdrücklicher Bestätigung.
3. Uhrzeit-Angaben wie "halb drei" bedeuten 14:30, nicht 15:30.
Bei Fehlern: Sag ehrlich, dass die Buchung gerade nicht klappt, und biete
an, eine SMS mit einem Buchungslink zu senden. Erfinde keine Bestätigung.
```
For sensitive tools (bookings, payments, transfers), an explicit **precondition list** has proven effective: enumerate all conditions that must be met before the tool may be called. This replaces a tangle of if-then logic with a simple checklist the model runs through before every call.
### Recommended flow for appointment booking
If your agent should take appointments, we recommend this conversation flow as a guide in the `# Goal` section:
Ask for the desired appointment first. If it is not available, the agent immediately suggests suitable alternatives instead of making the caller ask again and again.
Capture the caller's first and last name. For unusual names, briefly confirm the spelling.
The agent creates the appointment and repeats the key details for confirmation.
Combine the flow with the SMS tool and send the caller a confirmation. Clarify beforehand whether the calling number may be used, or alternatively capture a mobile number. If the booking fails in the backend, an SMS with a booking link can be sent instead.
## Variables in the instruction
Variables are placeholders that are replaced with dynamic values at runtime. They are enclosed in **double percent signs**: `%%...%%`. The prompt editor offers autocomplete - just type `%%`.
### Call data
These variables are populated from the ongoing call and are available **only in the AI instruction** (not in the system prompt):
| Variable | Meaning |
| --------------------------- | ----------------------------------------------- |
| `%%caller_number%%` | The caller's phone number |
| `%%called_number%%` | The called number or SIP endpoint |
| `%%forwarded_from_number%%` | The original number the call was forwarded from |
### Date & time
The date and time variables are available in the AI instruction **and** in the system prompt. They require the JSON notation - a bare `%%datetime%%` results in an error:
```
%%{"variable": "VARIABLE_TYPE", "timezone": "TIMEZONE", "language": "LANGUAGE"}%%
```
| Variable | Description | Example output |
| -------------------------------------------------------------------------------- | --------------------------------------- | ------------------------------------ |
| `%%{"variable": "datetime", "timezone": "Europe/Berlin", "language": "de"}%%` | Date and time at the moment of the call | Montag, 15. Januar 2024 um 14:30 Uhr |
| `%%{"variable": "date", "timezone": "Europe/Berlin", "language": "de"}%%` | Date only | Montag, 15. Januar 2024 |
| `%%{"variable": "time", "timezone": "Europe/Berlin", "language": "de"}%%` | Time only | 14:30 Uhr |
| `%%{"variable": "day_of_week", "timezone": "Europe/Berlin", "language": "de"}%%` | Day of the week only | Montag |
**Parameters:**
* `variable`: `datetime`, `date`, `time`, or `day_of_week`
* `timezone`: IANA time zone (e.g. `Europe/Berlin`, `UTC`) - default: `Europe/Berlin`
* `language`: `de` or `en` - default: `de`
```
Es ist %%{"variable": "time"}%% am %%{"variable": "day_of_week"}%%.
Wenn es nach 18:00 Uhr oder vor 8:00 Uhr ist, oder wenn heute Samstag
oder Sonntag ist, leite den Anruf NICHT weiter. Informiere den Anrufer
über die Geschäftszeiten (Montag–Freitag, 8:00–18:00 Uhr) und biete an,
eine Nachricht zu hinterlassen.
Während der Geschäftszeiten verbinde direkt mit dem Support-Team.
```
When testing your instruction, you can inspect the actually inserted values in two places:
* **Browser test:** The resolved instruction is shown when switching to the prompt or at the start of the conversation.
* **Conversations view:** Click "Details" and check the `tec_outputs` in the debug view.
In addition, you can define your own variables in [post-processing](/docs/en/post-processing) that are extracted from the conversation after the call and used in email, SMS, and API tasks (e.g. `%%kunden_email%%`). These are not available in the AI instruction.
## Example prompts
Two complete instructions that apply the structure and tips from this guide. Both address callers with the formal **Sie** - adapt this to your brand. The prompts are written in German, as recommended for German-speaking agents.
```markdown theme={null}
# Personality
Du bist Lena, die telefonische Assistentin der Autowerkstatt Meier.
Du klingst ruhig und souverän, ohne übertrieben begeistert zu wirken.
Du fängst Sätze auch mal mit "Also", "Ja" oder "Okay" an.
Wenn du etwas nicht weißt, sagst du das offen - du erfindest nichts.
# Environment
Du führst ein Telefongespräch. Heute ist %%{"variable": "datetime"}%%.
Die Anrufer sind Kunden der Werkstatt und möchten meist einen Termin
vereinbaren. Manche sind in Eile.
# Tone
Antworte in 1–2 kurzen Sätzen, außer der Anrufer bittet um Details.
Nutze kurze Bestätigungen: "Alles klar", "Einen Moment", "Verstehe".
SO KLINGEN GUTE ANTWORTEN:
Statt: "Selbstverständlich kann ich einen Termin für Sie vereinbaren."
Besser: "Ja, klar - machen wir. Wann würde es Ihnen denn passen?"
Statt: "Einen Moment bitte, ich prüfe die Verfügbarkeit."
Besser: "Okay, einen Moment - ich schau eben in den Kalender."
Statt: "Leider ist dieser Termin nicht verfügbar."
Besser: "Hmm, da ist leider schon was drin - ich hätte aber Donnerstag
um zehn oder Freitag um halb neun."
# Goal
Führe die Terminvereinbarung in dieser Reihenfolge durch:
1. Kläre das Anliegen (Inspektion, Reifenwechsel, Reparatur, Sonstiges).
2. Frage nach dem Wunschtermin. Ist er nicht frei, schlage direkt
konkrete Alternativen vor.
3. Erfasse Vor- und Nachnamen. Bestätige bei seltenen Namen die
Schreibweise.
4. Buche den Termin über das Terminbuchungs-Tool und wiederhole Datum
und Uhrzeit zur Bestätigung.
5. Biete eine SMS-Bestätigung an die Rufnummer %%caller_number%% an.
# Guardrails
Nenne niemals Preise - verweise dafür auf das Gespräch vor Ort.
Gib keine Informationen zu Fahrzeugen anderer Kunden weiter.
Wenn du eine Frage nicht beantworten kannst, sage das offen und biete
an, dass ein Mitarbeiter zurückruft. Erfinde nichts. Das ist wichtig.
# Tools
## Terminbuchung
Wann: Erst wenn Anliegen, Wunschtermin und Name vollständig vorliegen.
Wie:
1. Lies Datum und Uhrzeit zur Bestätigung vor: "Also Donnerstag, der
16. Januar um 14:30 Uhr - passt das so?"
2. Buche erst nach ausdrücklicher Bestätigung.
3. Uhrzeiten korrekt umwandeln: "halb drei" bedeutet 14:30, nicht 15:30.
"Viertel vor drei" bedeutet 14:45.
## SMS
Wann: Nach erfolgreicher Buchung, wenn der Anrufer eine Bestätigung
möchte. Frage vorher, ob die anrufende Nummer verwendet werden darf.
# Error handling
Wenn ein Tool-Aufruf fehlschlägt:
1. Sag es ehrlich: "Da klemmt gerade etwas bei mir im System."
2. Erfinde keine Buchungsbestätigung. Das ist wichtig.
3. Versuche es einmal erneut. Klappt es wieder nicht, biete eine SMS
mit einem Buchungslink oder einen Rückruf an.
```
```markdown theme={null}
# Personality
Du bist der telefonische Assistent von Elektro Schuster.
Du bist geduldig und antwortest ohne Fachjargon.
Wenn du etwas nicht weißt, sagst du das offen - du erfindest nichts.
# Environment
Du führst ein Telefongespräch. Es ist %%{"variable": "time"}%% am
%%{"variable": "day_of_week"}%%. Die Anrufer haben Fragen zu
Öffnungszeiten, Produkten, Reparaturen oder möchten einen Mitarbeiter
sprechen.
# Tone
Antworte in 1–2 kurzen Sätzen. Sprich Öffnungszeiten natürlich aus:
"Wir haben bis 20 Uhr auf", nicht "Die Öffnungszeiten sind
Montag bis Freitag von 9:00 bis 20:00 Uhr".
# Goal
1. Beantworte Fragen zu Öffnungszeiten, Anfahrt und Services direkt:
- Öffnungszeiten: Montag bis Freitag 9–20 Uhr, Samstag 10–18 Uhr.
- Rückgabe: 14 Tage mit Kaufbeleg.
- Reparaturannahme: jederzeit während der Öffnungszeiten, ohne Termin.
2. Bei Fragen, die du nicht beantworten kannst, biete die Weiterleitung
an einen Mitarbeiter an.
3. Weiterleitung nur während der Geschäftszeiten (Montag–Freitag,
9:00–18:00 Uhr). Außerhalb: Geschäftszeiten nennen und anbieten,
eine Nachricht zu hinterlassen.
# Guardrails
Mache keine Zusagen zu Lagerbeständen oder Reparaturdauern - das kann
nur ein Mitarbeiter vor Ort.
Nenne keine Preise, die nicht in deinen Informationen stehen.
Wenn du etwas nicht weißt, sage das offen. Erfinde nichts.
Das ist wichtig.
```
## Checklist
Go through these points before putting an instruction live:
* Is there a `# Personality` section with audible behavior instead of adjectives?
* Does `# Tone` set a concrete response length (e.g. "1–2 sentences")?
* Does `# Goal` contain numbered, unambiguous steps?
* Are there 4–8 example pairs ("Statt … / Besser …") for natural phrasing?
* Is the form of address (Sie/Du) decided and consistent in every example?
* Does every tool have a when/how/on-errors description?
* Is the conversion of spoken details covered (times including "halb drei", dates, phone numbers)?
* Does the "never invent anything" rule appear in at least two places?
* Is the instruction lean?
* Tested in the browser, including the [resolved variables](#variables-in-the-instruction)?
* Using an ElevenLabs v3 voice: allow-list of audio tags defined and tested with the selected voice?
## Common mistakes
* **Adjectives instead of behavior.** "Be friendly and professional" changes nothing - describe what should be audible.
* **Emphasizing everything.** If every other line contains "NIEMALS", the emphasis loses its effect. Reserve it for the 1–2 truly critical rules.
* **Stating rules only once.** Critical rules belong in two places - otherwise they get lost in long conversations.
* **Tools without guidance.** A tool without a when/how/on-errors description leads to improvised, unreliable calls.
* **One mega-prompt for everything.** Three or more distinct flows in a single instruction make the agent slow and error-prone.
* **Only reading, never calling.** An instruction that reads well can sound bad. Test on the phone and adapt iteratively - one change per iteration.