MCP preflight
A check an MCP client runs before it connects to a server and before each tool call: it asks for a signed decision about the server's domain and the action, and proceeds, warns, asks a person, or refuses. CrawlCheck publishes preflight middleware for the official TypeScript and Python MCP clients.
What MCP preflight does not show
A preflight decides whether to act on what is known now; it is not a security review of the server's code.
Terms this definition uses
MCP client · Tool call · preflight · Review
Related terms in Agents and protocols
How autonomous agents plan, remember, call tools and talk to each other, including MCP and A2A, and where each step can go wrong.
protected-resource metadata · token audience · PKCE · refresh token · default scope request · tool poisoning · tool lockfile · MCP rug pull · tool shadowing · agent manifest · stapled verdict · verdict over DNS · agentic web · preflight · decision receipt · receipt header · action assurance · resolve answer · freshness window · AI agent · Agent loop · Planner · Executor · Agent memory · Working memory · Long-term memory · Episodic memory · Semantic memory · Agent orchestration · Multi-agent system · Agent handoff · Delegation · Tool result · Tool schema · Tool description · Tool selection · Tool permission · Human-in-the-loop · Human-on-the-loop · Approval gate · Agent sandbox · Agent identity · Agent authorization · Agent discovery · Capability negotiation · MCP server · MCP client · MCP host · MCP resource · MCP prompt · MCP tool · MCP transport · JSON-RPC · A2A protocol · A2A client · A2A server · Agent skill · Agent task · Agent artifact · WebMCP · A2A
Questions about MCP preflight
What is MCP preflight?
A check an MCP client runs before it connects to a server and before each tool call: it asks for a signed decision about the server's domain and the action, and proceeds, warns, asks a person, or refuses. CrawlCheck publishes preflight middleware for the official TypeScript and Python MCP clients.
What does MCP preflight not show or guarantee?
A preflight decides whether to act on what is known now; it is not a security review of the server's code.
Which area of the glossary does MCP preflight belong to?
Agents and protocols: How autonomous agents plan, remember, call tools and talk to each other, including MCP and A2A, and where each step can go wrong.
← tool shadowing · agent manifest →
See it in the full glossary · 731 terms across 19 areas.