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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=true), and the description adds real behavioral value by disclosing exactly what is compared (hat code + seal vs. the hat as served now) and enumerating the full answer domain: verified, stale, cut-off, seal-missing, seal-wrong, pasted, not-worn. It stops short of explaining what a caller should do with each outcome.

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 sentences, front-loaded with the core check before the enumeration of outcomes; the outcome list is dense but each item earns its place. Minor jargon load ('hat code', 'seal') slows a first read but nothing is wasted.

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, the description correctly compensates by listing the possible verdicts, and the annotations cover safety and open-world behavior. What remains unstated is whether there is a cost/limit to checking, and how the caller should act on each verdict, so it is complete but not exhaustive.

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 100% so the two parameters are already documented, but the description adds meaning the schema does not: 'the hat as served now' clarifies that 'address' resolves to the live current hat, and 'the hat code and seal the reply quotes' explains the semantic link between the 'reply' string and the 'address'. That is genuine added context above the baseline 3.

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 ('Check') and resource ('whether a reply wore the current version of a hat'), and the mechanism (compares the quoted hat code and seal against the hat as served now) makes the operation concrete. It is distinguishable from wear_hat/wear_stack by being a read-only verification rather than a wearing action, though it never names those siblings explicitly.

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 framing implies you run this on a reply that quotes a hat, but there is no explicit when-to-use, no when-not-to-use, and no mention of the sibling tools wear_hat/wear_stack or how this fits after them. Guidance is left entirely to inference.

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