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

Beyond the readOnly/openWorld annotations, the description discloses billing mechanics ('$0.002 in USDC per call (x402 or prepaid credits)'), the free-trial status, and a neutrality policy ('we never resell them'), plus that reliability comes from the vendor's own checks. These are genuine behavioral facts the annotations do not carry, though latency or rate-limit behavior is not covered.

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 opening sentence and the third sentence ('Find the best tool for a job') restate the same purpose, and the title already carries the price, so there is some redundancy. The content is front-loaded and otherwise information-dense, keeping it from being wasteful overall.

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?

With an output schema present, return-value structure need not be described, and the description still previews what the list contains (what each does, how to use it, price, reliability, fit). For a four-parameter, single-required-input lookup tool with annotations covering safety, this is nearly complete; only routing guidance against the sibling x402 tools is missing.

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 job, kind, limit and maxPrice are already documented in the schema. The description adds only indirect hints (results are ranked, APIs and MCP servers returned 'side by side'), which loosely maps to the kind parameter but adds no syntax or semantics beyond the schema. 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?

The description gives a specific verb and resource: 'Describe a task and get the best pay-per-call APIs and MCP tools for it, ranked with prices and reliability.' An agent can tell what it returns. It does not, however, distinguish itself from near-identical siblings such as x402-find, x402-recommend, or x402-find-live, so sibling differentiation is absent.

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?

It provides concrete task examples ('check if a token is a rug pull', 'scrape a page to markdown', 'cheap LLM chat') and notes the free trial, which implies when to reach for it. But it never states when to use this over the similar x402-* siblings or what input it expects beyond plain English, so usage is only implied.

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