pymcp-sse
pymcp-sse is an asynchronous Python library to build Model Context Protocol (MCP) servers and clients that communicate over HTTP/SSE. It provides base classes for server/client, tool registration and discovery, server push/notification support with keep-alives, and a multi-server client abstraction. It also includes an LLM client abstraction for integration with LLM providers (e.g., an Anthropic Claude example).
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Security controls for the MCP transport (authz/authn, TLS requirements, rate limiting, etc.) are not explicitly documented in the provided README content. SSE over HTTP typically relies on HTTPS/TLS in deployment, but this is not stated as a requirement. The library uses common web/async dependencies (FastAPI/Uvicorn/httpx/SSE helpers); no dependency vulnerability status is provided here. LLM provider secrets are suggested via environment variables (ANTHROPIC_API_KEY), which is a positive signal, but comprehensive secret-handling/logging guarantees are not documented in the provided content.
⚡ Reliability
Best When
You want a lightweight Python MCP server/client implementation where SSE transport and async concurrency are convenient, and you can rely on your surrounding infrastructure for security controls.
Avoid When
You need comprehensive, explicitly documented auth, rate limiting semantics, retry/idempotency guidance, or production-grade operational guarantees that are clearly documented in the repository/docs.
Use Cases
- • Building MCP tool servers backed by FastAPI/Uvicorn that use Server-Sent Events for streaming/notifications
- • Creating MCP clients that discover tools and invoke registered MCP tools over SSE
- • Orchestrating connections to multiple MCP servers from a single client process
- • Implementing server-initiated notifications and keep-alive mechanisms in agent/chatbot ecosystems
- • Integrating MCP tool calling with an LLM provider via a provided LLM client abstraction
Not For
- • High-assurance/regulated deployments that require documented security controls like auth, audit logging, and formal threat modeling (not evidenced here)
- • Environments that require GraphQL/gRPC interfaces or standard OpenAPI contracts for the API surface (not evidenced here)
- • Use cases needing strict idempotency guarantees or transactional semantics for tool calls (not evidenced here)
Interface
Authentication
No explicit authentication mechanism for the MCP HTTP/SSE transport is described in the README content provided. LLM provider authentication is mentioned only for an example client (ANTHROPIC_API_KEY).
Pricing
Pricing for the library itself is not described; it is MIT licensed. Runtime costs depend on your hosted server and any LLM provider used.
Agent Metadata
Known Gotchas
- ⚠ Tool registration relies on type hints for describe_tools; missing/incorrect type hints may reduce tool schema quality.
- ⚠ SSE timeouts require alignment with keep-alive/ping intervals (README suggests read timeout > ping interval); misconfiguration can cause disconnects.
- ⚠ No explicit auth/rate-limit/idempotency/retry semantics were documented in the provided content, so agents may need to implement conservative retry/backoff and safety checks at the application layer.
Alternatives
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Scores are editorial opinions as of 2026-04-04.