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

With no annotations, the description carries the full burden and does well: it discloses the two auth paths (x402 with 402 payment instructions, or a free API key via param or REGISTRY_API_KEY) and the self-service key bootstrap. It does not cover rate limits, pagination, or result shape, which keeps it below 5.

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 tight sentences, front-loaded with purpose, then auth mechanics, then the keyless recovery path and sibling routing. Every clause is actionable and nothing is repeated.

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?

For a 6-param, all-optional search tool with no output schema, the definition covers auth, ranking basis, and fallbacks well. It could still say more about default result shape or pagination behavior, but no output schema exists, so the gap is modest.

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 description coverage is 100%, so the schema already documents sort, limit, category, protocol, min_score and api_key. The description adds only the api_key-overrides-env note, which the schema also states, so baseline 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?

States a specific verb (search) and resource (x402/MCP tools) and qualifies the ranking signal (real reliability data: uptime, latency, schema conformance). It also distinguishes itself from the sibling registry_lookup, so an agent can route without opening either schema.

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?

Explicitly routes alternatives: use registry_lookup for a quick free check of a known tool, and use registry_onboarding_message plus registry_create_api_key when no key exists. Both the when-to-use-this and when-to-use-something-else conditions are stated.

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