fast-agent
fast-agent is a Python CLI-first framework for interacting with LLMs and building coding agents, workflows, and evaluation pipelines. It supports MCP servers/clients (including stdio and streamable HTTP/SSE transports), shell-mode, interactive TUI prompts, and Python agent definitions (decorator-based) that can call MCP tools and chain workflows. It also includes MCP OAuth (PKCE) integration and optional MCP ping support.
Score Breakdown
⚙ Agent Friendliness
🔒 Security
Security-relevant details present in the README: OAuth for MCP uses PKCE and supports in-memory token storage (no tokens written to disk) plus optional OS keychain persistence via keyring. This reduces token leakage risk. However, TLS requirements and network security headers for any server-mode exposure are not explicitly documented in the provided text; dependency hygiene (CVEs) and actual token access controls are not verifiable from the provided content alone.
⚡ Reliability
Best When
You want a CLI and Python framework to orchestrate LLMs with MCP tool ecosystems, including interactive workflows and/or running locally with configurable transports and OAuth for MCP connections.
Avoid When
You need a stable, standardized REST/GraphQL/SDK surface for programmatic usage by other systems; you mainly want a turnkey managed cloud service with predictable SLAs.
Use Cases
- • Build coding/development agents that call MCP tools (LSPs, tool hooks, utilities).
- • Create and run multi-step agent workflows (chains, agent-as-tools orchestration, maker/voting error reduction).
- • Evaluate and test MCP-enabled agents and workflows.
- • Expose an agent as an MCP server using transport configuration.
- • Use interactive terminal experiences for agent prompting/completions/menus.
Not For
- • Simple single-purpose API wrappers where a REST/SDK interface is required.
- • Environments where opening OAuth flows and token storage via OS keychain is disallowed or cannot be configured.
- • Applications requiring strict server-side uptime/SLA guarantees without observing the project’s operational status.
Interface
Authentication
OAuth is described as enabled by default for SSE/HTTP MCP servers, configurable per server. The README discusses PKCE and token persistence behavior, but does not specify fine-grained scopes from the application perspective (it mentions optional server default scopes).
Pricing
No pricing model for the library/framework is described in the provided content. Costs depend on the selected LLM provider(s) and any MCP server backends.
Agent Metadata
Known Gotchas
- ⚠ CLI-first workflow: programmatic integration may require adopting their Python API/decorators or invoking the CLI rather than using a standardized REST interface.
- ⚠ MCP transport and OAuth behavior can vary by environment (e.g., keychain availability uses in-memory token storage), which may affect repeatability across sessions.
- ⚠ LLM/model/provider differences (and provider-specific model query overrides) may lead to inconsistent outputs if not pinned/configured carefully.
- ⚠ Chained/parallel tool calling can amplify failures if upstream MCP servers are unreliable; behavior under partial tool failures is not described in the provided material.
Alternatives
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Scores are editorial opinions as of 2026-03-29.