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

Annotations already declare readOnly, idempotent, openWorld and non-destructive, so safety is covered. The description adds genuinely useful behavioral context beyond that: results are real probed resources, each carries a measured 402 Score, and the call is free — none of which the annotations convey.

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 short sentences, front-loaded with the action and index identity, then the differentiator (verified/probed, scored) and the cost note. No filler.

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 structure needn't be explained, and the description covers scope, result trust, and cost. It could say slightly more about query semantics (multi-word, matching behavior) but is essentially complete for a two-parameter read tool.

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 both parameters (q, limit) are already documented in the schema, including defaults and example keywords. The description's mention of 'by capability' and examples largely duplicates the schema rather than adding syntax or validation detail, so baseline 3 applies.

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 (the Market402 verified index of x402 services) with the query dimension (by capability) called out. An agent immediately knows this is a capability-keyword search over a curated service catalog, distinct from every sibling tool listed.

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?

The phrase 'Search ... by capability' implies when to use it, and the examples ('ocr', 'market-data') guide query construction, but there is no explicit when-to-use/when-not statement and no named alternative among the many unrelated siblings. Usage is implied rather than specified.

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