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

Beyond the annotations (destructive, idempotent, not read-only), the description discloses the authorization model, the creator-scoped refusal case, the optimistic-lock contract, and the mismatch response ('the relay returns the current row, which is what a retry needs'). These are real behavioral traits the structured fields cannot express.

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?

Purpose is front-loaded in the first clause, and each subsequent sentence carries distinct information (permissions, concurrency, return shape). The permission sentence is dense with nested clauses, but nothing is redundant.

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, and the description closes the gap with 'Returns { row }' while also documenting the mismatch payload. For a 5-parameter mutation tool, an agent has everything needed: required inputs, authorization conditions, and concurrency semantics.

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 baseline is 3, but the description adds genuine meaning: it explains why if_match should carry the row's current version and what happens on mismatch, which goes past the schema's terse 'Optional optimistic-lock version.' The data parameter's replace-not-merge semantics are also reinforced.

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 opens with a specific verb+resource+scope: 'Update an existing row in a v2 app's collection, replacing its data,' and 'replacing its data' usefully signals full replacement rather than merge. It never names the obvious sibling upsert_row (create-or-update) or delete_row, so the agent must infer the boundary itself.

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 clearly states the conditions under which the call succeeds (update role list when declared, otherwise write list, with the creator-scoping example) and when to pass if_match for optimistic locking, including the retry path on mismatch. What's missing is explicit routing versus alternatives such as upsert_row for rows that may not exist.

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