whereismyai
Charter
Charter is an open-source Python library for building agent tools from API declarations and controlling agent interactions.
Charter is an open-source Python library designed to build agent tools directly from API declarations using Pydantic models. It runs in your process without proxies, per-call pricing, or telemetry, allowing you to manage what AI coding agents see, send, and receive across any HTTP API. The library handles authentication, supports per-user OAuth or API keys, and works with existing frameworks like LangChain, any OpenAI-compatible API, and the Model Context Protocol. Developers can shape schemas, control wire formats, pin values, and audit egress maps for security reviews. It provides ready-made tools across sixteen APIs and integrates directly into your existing infrastructure.
Charter at a glance
- Best for: Software engineer
- Runs on: Python, API, LangChain, MCP
- Pricing: Free and open source under the Apache 2.0 license.
- Released: September 2026
- Category: AI coding tool
- Website: github.com/r28ai/charter
Key features
- Build tools from API declarations using Pydantic models
- Shape and trim tool schemas to manage token costs
- Control outgoing wire formats and refuse bad arguments
- Trim incoming responses and handle false 200 status codes
- Manage per-user OAuth credentials and API keys
- Enforce egress maps and pin values for security
- Integrate with LangChain, OpenAI-compatible APIs, and MCP
Use it for
- Adding agent tools for Gmail, Stripe, or Notion with user OAuth
- Building and managing agent tools from API documentation
- Controlling token costs by curating and trimming tool schemas
- Auditing and reviewing agent data access and egress boundaries
Alternatives to Charter
- OpenCode — Works with 75+ model providers, local models, and existing subscriptions
- CopilotKit — Connects your application to AI agents with generative UI and human approvals.
- Google ADK — It applies software development principles to agent creation with Python.
- HarnessRouter — One API to manage agent runtimes, sandboxes, and execution lifecycles.
- fast-agent — Improves agent accuracy and cost efficiency via MCP integration.
- Agent Skills — Encodes senior-engineer workflows and quality gates into 24 skills.
- Tau — Read every moving part like a textbook with no hidden machinery.
- Kilo Code — Open-source agent with any model and no markup on inference
- Genkit — Provides unified APIs and local developer tools for AI application workflows.
- Agent Service Toolkit — Complete LangGraph agent service template, from agent to chat UI
- Agent Archive — Hand off coding sessions between Claude Code, Codex, and Cursor across machines.
- OpenAI Agents SDK — Provider-agnostic multi-agent framework with built-in guardrails and tracing.
All Charter alternatives