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

Beyond the annotations (readOnlyHint=false, destructiveHint=false), the description discloses three things the structured data does not: the operation is free, the credential type required (buyer secret), and the visibility rule that statements are 'visible to the operator only'. It does not mention that adding is non-idempotent, but the annotations already flag idempotentHint=false and the verb 'add' matches, so no contradiction.

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 short, front-loaded clauses covering constraint, cost, required inputs, and visibility. Nothing is padded and the size limit plus the access rule appear before the parameter recap.

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 simple three-parameter mutation with an output schema absent, the description covers auth, cost, size limits, and visibility, which is most of what an agent needs. It does not state what the call returns (e.g., a statement id) or confirm whether repeat calls create duplicates, so a small gap remains.

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 schema already documents all three parameters including the 1-2000 character bound on text and the agp_+32 hex format for secret. The description merely restates which inputs are needed, adding no syntax or format detail beyond what the schema provides.

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?

Specific verb+resource ('Add a statement to a deal') with actor scope ('as its buyer') and a hard size bound. It is clearly distinguishable from the sibling set, which all operate on deals (create/confirm/get/list) rather than on buyer-authored statements.

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 implies the caller must be the buyer's side of the deal via 'as its buyer' and tells the agent the operation is 'Free', which is useful framing. It never says when to prefer this over other deal tools or when not to call it, so guidance is implied rather than explicit.

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