# Prompts

> Version and manage your agent's prompts with LangWatch Prompts CLI. Use for both onboarding (set up prompt versioning for an entire codebase) and targeted operations (version a specific prompt, create a new prompt version). Supports Python and TypeScript.

- Skill: `langwatch/prompts` (Agent Skill)
- Install (CLI): `npx skillmds@latest add langwatch/prompts`
- Raw SKILL.md: https://api.skillmd.com/api/skills/langwatch/prompts/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: AI & ML
- License: MIT
- Author: langwatch (https://skillmd.com/u/langwatch)
- Updated: 2026-09-10
- Page: https://skillmd.com/skills/langwatch/prompts

---


# Version Your Prompts with LangWatch Prompts CLI

## Determine Scope

If the user's request is **general** ("set up prompt versioning", "version my prompts"):

- Read the full codebase to find all hardcoded prompt strings
- Study git history to understand what changed and why: focus on agent behavior changes, prompt tweaks, bug fixes. Read commit messages for context.
- Set up the Prompts CLI and create managed prompts for each hardcoded prompt
- Update all application code to use `langwatch.prompts.get()`

If the user's request is **specific** ("version this prompt", "create a new prompt version"):

- Focus on the specific prompt
- Create or update the managed prompt
- Update the relevant code to use `langwatch.prompts.get()`

In Langy, do not print the code change for the user to apply by hand: call `code_access` and follow the `code-changes` skill to make it on their machine or through GitHub.

## Plan Limits

LangWatch's free plan has limits on prompts, scenarios, evaluators, experiments, and datasets. When you hit a limit, the API returns `"Free plan limit of N reached..."` with an upgrade link.

How to handle:

- Work within the limits. If 3 resources of the relevant type are allowed, create 3 meaningful ones, not 10.
- Make every creation count: each one should demonstrate clear value.
- Show what works FIRST. If you hit a limit, summarize what was accomplished and note that upgrading the plan raises it. Point to the subscription settings on the platform, or to the license settings if the CLI is pointed at a self-hosted endpoint. Read the endpoint the CLI actually uses, which can come from `.env`, from the process environment, or from the saved CLI configuration.
- Do NOT delete existing resources to make room or repurpose an existing resource to evade the limit.

## Step 1: Read the Prompts CLI Docs

Then specifically read the Prompts CLI guide:

```bash
langwatch docs prompt-management/cli
```

CRITICAL: Do NOT guess how to use the Prompts CLI. Read the docs first.

## Step 2: Initialize Prompts in the Project

```bash
langwatch prompt init
```

Creates a `prompts.json` config and a `prompts/` directory in the project root.

## Step 3: Create a Managed Prompt for Each Hardcoded Prompt

Scan the codebase for hardcoded prompt strings (system messages, instructions). For each:

```bash
langwatch prompt create <name>
```

Edit the generated `.prompt.yaml` file to match the original prompt content.

**Model:** keep the generated `model` on a current model. Store the alias
`openai/latest` rather than a version number: LangWatch resolves it to the
current flagship at run time, so the prompt does not go a generation stale
every release. Do not default a new prompt to a legacy model like
`gpt-4o-mini`; pick one only when the user is trading quality for cost or
latency on purpose.

**Temperature:** the gpt-5 family rejects a custom `temperature`, so do not add
`modelParameters.temperature` for those models. `create` omits it on purpose.

**Structured outputs:** if the prompt must return strict JSON, add a
`response_format` block instead of asking for JSON in prose:

```yaml
response_format:
  name: product_category
  schema:
    type: object
    properties:
      category: { type: string }
      reasoning: { type: string }
    required: [category, reasoning]
    additionalProperties: false
```

`response_format` round-trips losslessly through `sync`/`pull`. See
`langwatch docs prompt-management/cli` for the full format.

## Step 4: Update Application Code

Replace every hardcoded prompt string with a call to `langwatch.prompts.get()`.

**Python (BAD → GOOD):**

```python
agent = Agent(instructions="You are a helpful assistant.")
```

```python
import langwatch
prompt = langwatch.prompts.get("my-agent")
agent = Agent(instructions=prompt.compile().messages[0]["content"])
```

**TypeScript (BAD → GOOD):**

```typescript
const systemPrompt = "You are a helpful assistant.";
```

```typescript
const langwatch = new LangWatch();
const prompt = await langwatch.prompts.get("my-agent");
```

CRITICAL: Do NOT wrap `langwatch.prompts.get()` in a try/catch with a hardcoded fallback string. The whole point of prompt versioning is that prompts are managed externally. A fallback defeats this by silently reverting to a stale hardcoded copy.

## Step 5: Sync to the Platform

```bash
langwatch prompt sync
```

## Step 6: Tag Versions for Deployment

Three built-in tags: `latest` (auto-assigned), `production`, `staging`. Update code to fetch by tag:

```python
prompt = langwatch.prompts.get("my-agent", tag="production")
```

```typescript
const prompt = await langwatch.prompts.get("my-agent", { tag: "production" });
```

Assign tags via the CLI (or the Deploy dialog in the LangWatch UI):

```bash
langwatch prompt tag assign my-agent production
```

For canary or blue/green deployments, create custom tags with `langwatch prompt tag create`.

## Step 7: Verify

Run `langwatch prompt list` to confirm everything synced, or open the Prompts section in the LangWatch app.

## Common Mistakes

- Do NOT hardcode prompts. Always fetch via `langwatch.prompts.get()`
- Do NOT add a hardcoded fallback string in a try/catch; that silently defeats versioning
- Do NOT manually edit `prompts.json`. Use the CLI
- Do NOT skip `langwatch prompt sync` after creating prompts
- Prefer the flagship alias `openai/latest` (or `openai/latest-mini` for the fast tier). Pin a version only when a prompt is tuned to one, and pick an older model like `gpt-4o-mini` only when intentionally optimizing for cost or latency
- Do NOT set `modelParameters.temperature` on a gpt-5-family model; the family rejects it
- Do NOT ask for JSON in the prompt text when output must be structured. Use a `response_format` block