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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description adds the cost signal ('Free rail') and the ordering constraint ('Call first'), which is real value beyond the annotations, but 'Free rail' is cryptic and no behavior like caching or rate limits is spelled out.

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 short sentences, front-loaded with the core action and its payload, with the imperative 'Call first' leading the second sentence. Slightly hurt by the undefined shorthand 'the seven invariants' and the opaque 'Free rail', which cost clarity for the sake of brevity.

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?

The tool is simple (no params), annotations cover the safety profile, and an output schema exists so return values need not be described. The description lists the content categories, which is enough for an agent to decide to call it; only the meaning of 'seven invariants' and 'Free rail' remains unexplained.

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 and the schema is empty, so there is nothing for the description to disambiguate. Baseline of 4 applies; no parameter-level detail is needed or missing.

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?

States a specific verb (describe) and resource (the method), then enumerates the payload: formulas, constants, defaults, statuses, invariants, citations and limits. That is enough for an agent to know this is a self-documentation/read-me endpoint. It does not distinguish itself from siblings like explain_valuation or verify_receipt, which is why it stops short of 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?

'Call first' is explicit ordering guidance that tells the agent to invoke this before the sibling tools, which is genuinely useful. However, there is no statement of when NOT to use it, nor any reference to alternatives (explain_valuation, simulate_pool, value_site, verify_receipt) other than the implicit ordering.

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