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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds valuable operational context: 'no fees, no auth,' which helps the agent understand cost and access requirements beyond the annotations. It does not describe validation result semantics, but the output schema mitigates that gap.

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 description is a single, information-dense sentence with no filler. It front-loads the core purpose ('Free pre-flight validation'), includes the operational caveats ('no fees, no auth'), and ends with the key routing instruction to the sibling tools.

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 validation tool, the description captures everything an agent needs before invocation: what it validates, that it is free and auth-free, and exactly when to use it. The rich input schema and presence of an output schema cover the details of what to pass and what to expect in return, so nothing essential 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 the input schema already thoroughly documents all parameters, including nested listing and proposal objects. The description adds no extra parameter-level meaning beyond indicating that both 'listing' and 'proposal' kinds are supported, which is acceptable given the schema does the heavy lifting.

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 uses a specific verb ('validate'), names the exact resource ('listing or proposal'), and positions it as 'pre-flight validation' against platform schemas. This clearly differentiates it from siblings like market_post_listing and market_propose, and the title reinforces the purpose without ambiguity.

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 description explicitly says 'Always validate before market_post_listing or market_propose,' providing direct, unambiguous guidance on when to use this tool versus its mutation siblings. This leaves no room for an agent to call post/propose without validating first.

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