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

Beyond the annotations (readOnly, openWorld, idempotent, non-destructive), the description discloses the exact output structure ({ title, implied_probability, url }), the meaning of implied_probability (main/YES outcome or top outcome for multi-outcome markets), and the 'Keyless' auth requirement. This adds substantial behavioral context beyond the structured fields.

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: the first gives the primary action and output, the second provides usage guidance, and the third clarifies probability semantics. Every sentence contributes value with no redundancy or padding.

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?

Despite no output schema, the description fully specifies the return format and field semantics. It includes usage context, authentication ('Keyless'), and probability interpretation. This is complete for a simple top-5 fetch tool, especially with strong annotations covering safety.

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% with both 'query' and 'venue' described. The description only echoes these parameters without adding new semantics (e.g., format, examples, or edge cases). Therefore, the baseline of 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?

The description starts with 'Single-venue drill-down: fetch one venue's current top 5 matches for a query', which clearly states the verb (fetch), resource (venue's top 5 matches), and scope (single-venue). It distinguishes from siblings like compare_topic by emphasizing single-venue focus.

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 'Useful after compare_topic to look closer at one venue', providing a clear when-to-use context and naming an alternative workflow. It doesn't explicitly state when-not-to-use, but the single-venue scope implicitly excludes multi-venue comparisons.

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