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

Annotations already communicate read-only and non-destructive behavior. The description adds meaningful behavioral context beyond that: the paid nature (US$0.02 per successful call or 1 Horse Truth credit) and the constraint that exactly one named signal is returned. No contradiction with annotations exists.

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 concise and front-loads the critical payment condition before the core purpose. The example signal list is compact but useful. Minor jargon like 'x402 call' and 'Horse Truth direct credit' is unexplained, slightly reducing clarity.

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 no output schema and minimal parameter documentation, the description leaves key gaps: what the returned signal looks like, how the horse should be identified, and how this tool relates to siblings. The pricing detail is useful, but the overall definition is not complete enough for confident autonomous invocation.

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 0%, so the description must compensate, but it only partially does. It gives example signal names that mirror the enum, but does not define what each signal means or clarify what form the 'horse' parameter should take. The agent gains little semantic clarity beyond the schema itself.

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 clearly states the tool's action ('Return') and resource ('one named derived Horse Truth signal for a horse'), with concrete example signals. It is specific and understandable, though it does not explicitly distinguish itself from siblings like horse_snapshot or horse_intelligence.

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 gives no guidance on when to use this tool versus sibling tools, nor does it mention prerequisites, exclusions, or alternative selection criteria. It only describes what the tool returns, leaving the appropriate invocation context to inference.

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