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

Annotations already flag destructiveHint=true and idempotentHint=false, and the description adds substantive context beyond them: irreversibility ('cannot be undone'), the recipient/scheduling preconditions, and the paid-account requirement. It also names the underlying endpoint, which helps with debugging and traceability.

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 compact and front-loads the destructive nature of the call, which is the right priority. The shouty capitalized opening ('WRITE, SENDS EMAIL TO CUSTOMERS NOW') is slightly awkward and mildly redundant with the following clause, costing a point.

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?

With only two parameters, full schema coverage, and no output schema to explain, the description covers everything an agent needs: what it does, when it may be called, what approval is required, and that it is irreversible. Nothing material is missing.

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%, and both parameters are documented in the schema itself, so baseline is 3. The description reinforces confirm's meaning as user approval but adds no syntax, format, or edge-case detail beyond what the schema already 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?

The description states a specific verb-and-resource pair ('sends / delivers the campaign to its assigned recipients immediately') and pins the timing with 'NOW', which clearly separates it from create_campaign, get_campaign_stats, and send_transactional_email. An agent can identify the operation without reading the schema.

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 lays out explicit preconditions: at least one recipient, not already scheduled or delivered, a paid account, and prior user approval with confirm set to true only after that approval. It also states the sequencing rule (show the campaign and audience, get go-ahead, then send), leaving nothing to inference.

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