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

Annotations cover the safety profile (readOnly/idempotent/non-destructive/openWorld), and the description adds real context on top: metered, delayed usage tied to the connected account, a single bounded request with no polling or auto-retry, affiliate 27 excluded, and the warning not to infer coverage from an empty result. That is materially more than the structured fields provide.

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 definition crams many clauses into a near run-on with missing punctuation ('...market definitions Returns all...'), mixing purpose, caveats, and disclaimers. It is front-loaded with the purpose, which helps, but several sentences (e.g. the wager/returns disclaimer) add limited value.

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?

Because an output schema exists the description needn't explain return values, and annotations carry the safety profile, so the remaining needs are scope and operational caveats — which the description supplies (metering, retry, affiliate exclusion, empty-result caution). It is close to complete, with sibling differentiation the only notable gap.

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?

The tool takes zero parameters, so there is no syntax to document and the baseline is 4. The listed output fields are redundant with the existing output schema rather than adding new parameter meaning.

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 ('List all market definitions') and enumerates the returned fields (IDs, names, period info, participant flag). It does not, however, differentiate itself from overlapping siblings such as list_markets, v2GetMarketsByDate or v2GetAvailableMarketsByEvent, so an agent cannot tell from the text alone when this unfiltered variant is the right pick.

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?

'Use returned canonical IDs' and 'Read-only Product data or price calculation' imply a usage context, and the empty-result caveat is useful. But there is no explicit when-to-use/when-not guidance and no named alternative, so routing versus the many list_/v2GetMarkets* siblings is left to inference.

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