Turning OpenAPI Specs into Runtime LLM Tools in Pi

Gino Tesei — Thu, 14 May 2026 03:12:34 +0000

I built pi-openapi-tools — a Pi extension that reads an OpenAPI/Swagger spec and dynamically registers one callable tool per API operation.

Instead of hand-writing wrappers for every endpoint, you point Pi at a spec URL and immediately start using generated tools.

Why I built this

Most API-agent integrations still require too much manual glue code:

That slows experimentation and makes agent tooling fragile.

I wanted a runtime-first workflow:

spec → generated tools → live API calls

What the extension does

Given an OpenAPI or Swagger spec URL, pi-openapi-tools:

It also includes:

60-second quickstart

Install:

pi install npm:pi-openapi-tools

Generate tools from Petstore:

/swagger-tools https://petstore.swagger.io/v2/swagger.json --prefix pet
/swagger-tools:list

You’ll immediately get generated tools such as:

A few implementation details mattered a lot in practice:

Prefix-scoped additive registration
Multiple API toolsets can coexist cleanly.
Stable naming + dedupe
Generated names are sanitized and collision-safe.
No unregister support in Pi? Stub instead.
Removed tools become non-executable guidance stubs instead of silently disappearing.
Content-type-aware serialization
Request body handling follows declared spec media types (JSON, form-data, urlencoded, text, etc).

I also added a full walkthrough + simulation test:

If you try it on large or messy specs, I’d especially love feedback on:

If this is useful, feel free to star the repo and share your API use case.

DEV Community: Gino Tesei