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

With annotations present, the description still adds real value: it discloses the privacy model ('We never see or store the document — only the hash'), the response shape, and explicit scope disclaimers (not legal proof, notary, evidence, or a certificate). It does not address idempotency behavior despite idempotentHint=false, but the privacy and scope disclosure goes well beyond the annotation set.

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 return shape is front-loaded in the first clause, followed by the input constraint, privacy note, and disclaimers. Every sentence carries information, though the disclaimer sentence is long and slightly dilutes the core call instructions.

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?

There is no output schema, so the description appropriately enumerates the returned fields and explains the trust model behind them. Combined with the schema's api_key documentation, an agent has what it needs, though auth requirements and any cost/rate behavior are not stated.

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%, so the baseline is 3; the description earns a point by reinforcing the strict input contract ('Send ONLY a SHA-256 hex digest (64 characters)') and clarifying that the document itself is never sent. The optional api_key is left entirely to 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 states a specific verb and resource: it returns a signed receipt (sha256, stamped_at, key_id, signature, public_key_url) attesting that a booklint-family service saw the hash at a given time. That is far more than a restatement of the name. It does not explicitly contrast with the sibling verify_receipt, so it falls short of a 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?

It gives a clear input rule ('Send ONLY a SHA-256 hex digest (64 characters)') and an implicit purpose, but never states when to use stamp_hash versus verify_receipt, or any prerequisites such as whether a key is required. Usage is implied rather than guided.

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