x402-discovery-mcp

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

Annotations establish the operation is read-only and idempotent, but the description adds crucial cost transparency (the $0.010 fee) and output format details (quality-ranked results with uptime%, latency, code snippets) not present in the annotation hints. It also adds meta-context that the tool 'demonstrates the exact protocol it helps you discover.'

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 tightly constructed sentences each serve distinct purposes: (1) core function, (2) return value payload, (3) cost disclosure and meta-protocol context. Front-loaded with the action verb, zero redundancy, and appropriately sized for the complexity.

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?

Given the presence of an output schema, the description appropriately summarizes rather than enumerates return values. The cost disclosure is critical completeness for a paid tool. The only gap is the lack of parameter documentation given the 0% schema coverage, though the unique protocol context (x402 micropayment) is well-covered.

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?

With 0% schema description coverage, the description must compensate for undocumented parameters. It implicitly covers 'query' (keyword) and 'capability' but fails to explain 'max_price_usd' or 'min_quality' filtering parameters, leaving their semantics and relationship to the results unclear without schema inspection.

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?

The description provides a specific verb ('Find') and resource ('x402-payable services') and distinguishes the scope (by capability or keyword) from siblings like x402_browse or x402_register. It clearly identifies this as a service discovery operation within the x402 ecosystem.

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?

The description provides critical usage context by disclosing the micropayment cost ($0.010 USDC per query), which is essential for an agent to decide whether to invoke the tool. However, it lacks explicit guidance on when to use this versus sibling tools (e.g., 'use browse for unfiltered exploration, use discover for targeted search').

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