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

With no annotations the description carries the full burden, and it does disclose significant behavioral facts: the operation is a search/read, results come from two named sources, and it costs $0.02/call in USDC on eip155:8453. Pricing for a paid API is exactly the kind of context annotations would never carry. It doesn't state return shape or pagination, and there's no output schema, so it falls short of a 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?

Front-loaded with the core behavior and price, and every sentence adds something. However, the fragment 'Use this when an agent needs to "I need a tool that does X" → matched paid APIs' is grammatically awkward and the meta-tool sentence partly restates the opening.

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 three-param search tool with no output schema, the description covers what it searches, the two sources, the cost, and when to reach for it. Return format is unstated, but that is the main remaining gap and is not critical for invocation.

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 query, includeBazaar, and limit; baseline is 3. The description only adds that Bazaar inclusion is optional, which the enum already conveys.

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+resource: describe a need, get back matching x402-paid APIs, from a named catalog (54 tools) plus the optional Bazaar. The meta-tool framing clearly separates it from every sibling, which are all concrete capability tools.

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?

"Use this when an agent needs to 'I need a tool that does X'" gives an explicit triggering condition, and "instead of knowing an API exists, ask for the capability" distinguishes it from directly invoking a known sibling. It stops short of naming explicit exclusions or alternatives, so not a 5.

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