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

Annotations already declare readOnly/idempotent/openWorld/non-destructive, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: a $0.001 USDC per-call cost, the thirty-day ranking window, and byte-identity with a known REST endpoint. It stops short of noting rate limits or pagination behavior.

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 sentences, front-loaded with what is returned, then when to use it, then operational facts (cost, endpoint equivalence). No filler and nothing repeated from the schema or annotations.

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?

An output schema exists, yet the description still summarizes the returned fields and discloses the per-call cost and ranking window — everything an agent needs to select and call this correctly. The only loose end is the limit=20 vs. schema default=10 discrepancy, which is minor.

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% for the single 'limit' parameter, so the schema already carries the semantics (max 50, default 10) and the baseline is 3. The description's only parameter-relevant statement is the endpoint equivalence at limit=20, which arguably conflicts with the schema's stated default of 10 rather than clarifying it.

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: hosts actually receiving calls on the x402 rail, ranked by thirty-day call count, with the exact fields returned (unique-payer count, listed resources, highest advertised price). An agent can distinguish this from directory-style or aggregate siblings (market_x402_overview, market_x402_host_demand, market_x402_payer_bands) from the description alone.

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 says when to use it: 'to see who is earning and at what price point, instead of guessing from a directory,' which contrasts with directory/listing approaches. It does not name the specific sibling tools (e.g., market_x402_host_demand, market_x402_payer_bands) that an agent might confuse it with, so routing between x402 siblings still requires inference.

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