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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false. The description adds behavioral nuance beyond these: exact matching against stored fields, the optional 'sha256:' prefix, and the critical caveat that the response always reports cryptographically_verified: false. This prevents a major misunderstanding, though it doesn't cover all possible edge cases (e.g., not found behavior).

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 tight three sentences: first states the action and target, second provides format and matching details, and third clarifies a likely misconception. No wasted words, all information is pertinent, and it is front-loaded with the key verb and object.

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 single-parameter, read-only lookup tool with robust annotations and an output schema, the description covers all necessary aspects: purpose, input format, matching behavior, and a warning about common confusion. There are no missing behaviors that an agent would need to know for correct invocation.

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 covers the single parameter fully (100% coverage) with a description including the 64-hex requirement and optional prefix. The description reinforces the format and clarifies matching semantics ('matching is exact against the stored receipt_hash/entry_hash fields'). It adds a slight enhancement over the schema by linking the parameter to both hash fields, but the core semantics were already well-documented in the schema.

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 uses a specific verb+resource construction: 'Look up a NOMOS operation record by its exact SHA-256 receipt hash in the local handshake audit log.' It clearly differentiates from cryptographic verification, which is a likely point of confusion, and leaves no ambiguity about its scope (exact-match lookup).

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 explicitly states when to use the tool (exact receipt hash lookup) and firmly excludes misuse ('NOT cryptographic signature verification'). While it doesn't name an alternative tool, the negative guidance plus the format requirement ('Requires a full 64-hex hash') gives clear usage context. A minor gap is the absence of a mention of an alternative tool for verification.

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