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

readOnlyHint=true confirms the safe-read nature, and the description adds real substance beyond that by disclosing the verification criteria (signer identity, immutability, freshness). However, with no output schema it never says how a verdict is delivered — boolean, thrown error, or structured result — nor what "fresh" is measured against, which is the single most important behavioral fact for a verifier.

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 definition and ending on an actionable directive; there is no filler. The phrase "Act only on valid and fresh" is slightly elliptical — it assumes the reader knows the verdict vocabulary — but it earns its place as the operative rule.

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 one-parameter verification tool with a nested signal object and no output schema, the definition covers what is checked but not how the check resolves or how a failure surfaces. An agent can call it correctly but cannot predict what it receives back, which is a meaningful incompleteness for a gate-style tool.

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 100% and the single `signal` property is already documented as coming "from an event or mandate_signal." The description adds no syntax, shape, or provenance detail beyond that, so the baseline 3 for a fully documented single-parameter schema is correct.

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 ("Checks") and a specific resource ("a mandate signal") and enumerates the three properties verified: signature by Actuary, integrity ("nothing in it changed"), and freshness. That is far more discriminating than the title alone. It does not, however, contrast itself with the similarly named sibling verify_receipt, so the agent must infer which verifier applies to which artifact.

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 closing imperative "Act only on valid and fresh" implies the tool is a gate to be run before acting, which is genuine usage guidance. But there is no explicit when-to-use versus when-not-to-use framing, no statement about whether it must be called before every action or can be cached, and no routing to verify_receipt for the receipt case — usage remains implied rather than stated.

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