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

Annotations already mark the operation as read-only and non-destructive. The description adds valuable behavioral context beyond annotations: the payment requirement (US$0.02 per call or 1 Horse Truth credit) and the receipt-based output nature. No contradiction with readOnlyHint.

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, efficient sentence with no filler. However, the payment note is front-loaded ahead of the actual functional purpose, and 'PAID:' reads as a separate label rather than part of a natural flow.

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 zero parameter documentation, the description is incomplete for a tool that requires a correctly formatted 'horse' argument. It also lacks any usage context relative to the ten sibling tools, leaving the agent to guess when this receipt tool is the right choice.

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 schema shows a single required 'horse' string with 0% description coverage, and the description does not explain what 'horse' should contain (ID, name, URL, etc.). The tool cannot be invoked correctly without this information, and nothing in the description compensates for the gap.

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 specific action ('Return a cryptographic receipt') and a specific resource ('the current derived horse-intelligence payload'), which clearly signals this tool produces a receipt, not the payload itself. This differentiates it from siblings like horse_intelligence and horse_snapshot, though the phrase 'current derived horse-intelligence payload' is somewhat jargon-heavy.

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 includes cost/payment information but provides no guidance on when to use this tool versus a sibling like horse_intelligence or horse_snapshot. There are no explicit conditions, exclusions, or alternative routing cues.

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