x402-discovery-mcp

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Adds substantial context beyond annotations: specifies EdDSA JWT format, enumerates attestation contents (uptime, latency, health, compatibility), and details offline verification method using JWKS endpoint. Annotations cover safety profile (readOnly, idempotent, openWorld), description covers data semantics and verification workflow.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Three dense sentences with zero waste: (1) core action + format, (2) content details, (3) verification instructions + spec reference. Front-loaded with essential operation details. Appropriate technical density for blockchain/identity context.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Strong coverage of output characteristics (JWT format, signature mechanism, spec compliance) given output schema exists. References specific ERC standard for protocol context. Only gap is parameter documentation, but overall adequate for a 2-parameter read operation with rich annotations.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema has 0% description coverage. Description partially compensates by implying 'service_id' through 'for a registered x402 service', but 'raw' boolean parameter is completely undocumented—no indication whether it returns raw JWT vs decoded payload vs other format. With 0% coverage, both parameters needed explicit semantic documentation.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Specific verb 'Fetch' with clear resource 'signed discovery attestation (EdDSA JWT)'. Distinguishes from siblings (browse/discover list, health checks status, register creates) by specifying cryptographic attestation purpose. Mentions specific content (uptime %, latency) that differentiates output nature.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

Provides implied usage context through 'signed discovery attestation' and ERC-8004 coldStartSignals spec reference, suggesting use for cryptographic verification scenarios. Lacks explicit when/when-not guidance or named sibling alternatives (e.g., 'use x402_health instead for simple status checks').

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.