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

Goes well beyond the annotations by disclosing the cost model: $0.002/call via x402 USDC or a card key, first 25 free, failed calls free, and that each call is charged so repeats are not free. This is exactly the kind of economic and auth context annotations cannot express, and the 'repeats are not free' note is consistent with idempotentHint=false.

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 purpose and the catalog scope, with pricing and the example trailing correctly. The body is a dense multi-clause sentence with a parenthetical category list that slows reading, but no clause is genuinely dead weight.

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 2-parameter discovery tool with no output schema, the description covers catalog breadth, the shape of each recommendation, cost and free tier, and the read-only nature of the call. An agent has everything needed to invoke it and interpret the result without opening anything else.

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 both parameters are already documented; the baseline is 3. The description adds value by showing a real 'need' value, illustrating the expected phrasing and specificity, though it says nothing about the count parameter beyond what the schema states.

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 and resource: turn a plain-language task into best-matching paid API calls from a 320-item catalog, and enumerates the return fields (call URL, required inputs, price, MCP tool name, free-call status). It is unmistakably distinct from the utility siblings (base64_encode, calc_tip, uuid), which do work rather than recommend 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?

Explicit triggering condition: 'Use when an agent needs to find which API to call before paying for one', which also implies the ordering constraint (recommend first, then pay). A concrete worked example ('need=current gas price on Base') removes ambiguity about the granularity of a 'task'.

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