Discover paid APIs (x402 + MPP)

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

With no annotations provided, the description fully discloses behavior: it queries a local curated registry and external indexes when federation is enabled, explains the 'source' field (verified vs. unverified), and the 'protocol' field (x402 or mpp). No destructive actions are implied.

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?

The description is four sentences, each serving a distinct purpose: core function, external indexes, source field, and protocol field. No redundant or extraneous information.

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 absence of output schema and annotations, the description covers the tool's purpose, federation behavior, and key response fields. It is slightly lacking details on error handling or pagination, but overall provides sufficient context for an AI agent to use the tool correctly.

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 coverage is 100%, so the schema already describes both parameters adequately. The description adds no significant new meaning beyond what is in the schema (e.g., 'free-text' repeats the schema description for query, and limit defaults are restated). Baseline of 3 is appropriate.

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 clearly states the tool searches a registry of paid APIs by free-text query, using the verb 'Search' and specifying the resource. It distinguishes itself from siblings 'pay.fetch' and 'pay.wallet_status' by focusing on discovery versus retrieval or status checking.

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?

No explicit guidance on when to use this tool versus alternatives (e.g., pay.fetch). The description does not include when-not-to-use scenarios or suggest alternative tools, leaving the agent without clear selection criteria.

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