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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the description need not repeat that. It adds the payment cost (US$0.02 per call or 1 Horse Truth credit), which is important behavioral context. However, it does not describe the format of change events or any filtering behavior beyond 'material'.

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 with two sentences, front-loading the payment information. It is well-structured and easy to read, though the second sentence is terse and could be expanded without losing conciseness.

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 tool with 2 parameters and no output schema, the description is incomplete. It lacks explanation of the limit parameter, the meaning of 'material', and the return format. Given the low schema coverage, more detail is needed for an agent to call it correctly.

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 0%, so the description must compensate. It only mentions 'for one horse' which implies the horse parameter, but does not explain the limit parameter or the format of the horse identifier. The description adds minimal meaning beyond the schema.

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 states a clear verb 'Return' and resource 'Horse Truth change events' for one horse, distinguishing it from siblings like horse_snapshot (snapshot) and horse_compare (comparison). However, the term 'material' is vague and could be interpreted differently, so it's not a perfect 5.

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?

No guidance on when to use this tool vs alternatives. It does not mention any conditions, exclusions, or comparisons to sibling tools. The description only states what it does, not when to prefer it over others.

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