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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: no paid entitlement is consumed and no raw provider records are exposed, plus the fact that the returned proof is fixed. That is useful cost and data-exposure disclosure beyond the annotations, though rate limits and return shape are not covered.

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?

Two compact sentences with the key qualifier ('FREE') front-loaded. Slightly dense jargon in the second clause costs it the top mark, but nothing is padded or repeated.

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 input parameters and no output schema, the description carries the return-value burden and does name two returned elements (the proof and the cheapest exact paid next actions). It is adequate for a simple read-only preview, though the undefined term 'Horse Truth proof' leaves the exact payload shape somewhat opaque.

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 the baseline is 4; there is nothing for the description to disambiguate. It correctly implies the call is self-contained (a fixed horse, no inputs needed).

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 names a specific verb ('Return') and a concrete payload ('a fixed real derived Horse Truth proof for Chance With Wolves plus the cheapest exact paid next actions'), so it is more than a tautology. However, the phrasing is cryptic jargon ('fixed real derived Horse Truth proof') and it never distinguishes itself from siblings like horse_snapshot or horse_intelligence, leaving the agent to guess what 'preview' actually yields.

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 'FREE' framing and 'No paid entitlement is consumed' clause imply the usage context: reach for this when you want a preview without spending entitlement. That is implied guidance rather than explicit when/when-not/alternative routing, and no sibling is named as the paid counterpart.

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