Charter
github.com/r28ai/charter- Category
- Developer Tools
- Rank
- No. 1938Tools index
Previous survey · No. 1912 ·
- Pricing
- Open Source
- Type
- TOOL
- Use case
- Agent Building
- GitHub
- 5 stars
- Latest release
- v0.6.0
- Date
About
Charter is a Python library that lets developers declare AI agent tools as Pydantic schemas instead of writing implementation code; the model fills in the arguments and Charter handles the request, authentication, and wire format. It ships 549 tools across fifteen APIs, runs in-process as a library rather than a hosted proxy service, and has no per-call pricing or telemetry.
At a glance
Charter is a Python library that validates an agent’s HTTP tool calls before sending them. It is worth evaluating if your app acts for several customers and needs to supply the account identity itself while letting the model fill in selected fields.
Good fit
Python developers who own the agent executor and want reviewable rules for API calls.
Consider something else when
Skip it if your agent can reach the same API through other routes you cannot control.
Start here
Define a mock order lookup for two synthetic customers. Supply the customer ID from your app and ask for an order from each account. Verify that only the permitted request reaches the test endpoint.
Cost and requirements
Apache-2.0. Requires Python 3.10 or later, Pydantic and HTTPX. It runs in your process. Charges for the model or destination API are separate.
Limits to know
Your application supplies the trusted identity and writes the ownership check. The declaration controls calls routed through Charter. Keep authorization at the destination API as well.
Sources checked 2026-11-05. Source-based assessment.
Why it made the leaderboard
It collapses the usual per-API glue code needed to expose tools to agents into a schema declaration, cutting integration time for anyone wiring agents to real-world APIs.
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Editorially curated, with community endorsements as a secondary signal. Corrections welcome.