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

Annotations only say it is a non-readonly, non-destructive write; the description adds the substance: the open-items register gates the call, a computed close is required, the actor must be the principal rather than the client, and the signature is what releases the workpapers. That is genuine side-effect and authorization context beyond the structured hints.

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?

Three tight sentences: what it does, the refusal conditions, then the actor constraint and consequence. Front-loaded and free of repetition.

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 mutation with no output schema, the definition covers preconditions, authorization, and the downstream effect on workpapers. It does not say whether signing is idempotent, whether it can be retracted, or what the response contains, which leaves a modest gap.

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% for the single engagement_id parameter, so the baseline is 3. The description adds a meaningful clarification that the signer is not a parameter because the identity is the authenticated principal, which prevents an agent from searching for a signer field.

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 (signs) against a specific resource (the governed close) with scope (per engagement, by name, on the engagement file) and actor (the principal). It distinguishes itself from the neighboring compute/agreement tools by tying the signature to a previously computed close.

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?

Preconditions are spelled out concretely: it refuses while any open item remains, and a close must already have been computed, which implicitly routes the agent to open_items and compute_close first. A constraint on who may sign (not on the client's behalf) is also given. It stops short of naming the prerequisite tools explicitly.

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