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

Goes well beyond the annotations by disclosing three non-obvious behaviors: sending is refused when the address has opted out, the message is recorded on the lead, and a new lead is auto-moved to contacted. These are exactly the side effects and failure modes an agent needs before invoking a destructiveHint=true mutation.

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?

Four short sentences, all front-loaded with the action first, then the prerequisite, then the constraints and side effects. No filler.

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 4-required-param mutation with no output schema, the description covers prerequisites, refusal conditions, and resulting state changes, so an agent can call it safely and predict its effects. Nothing essential 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 coverage is 100%, so the baseline is 3; the description adds value by clarifying what is NOT a parameter (the recipient address) and by requiring the mailbox to be verified. It doesn't describe subject/body constraints, but the schema already covers those.

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 (send one email), the resource (a lead), the constraint (from a verified mailbox), and the side effect (recorded on the lead). The word 'email' also implicitly separates it from send_lead_sms without naming it.

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?

Gives concrete operational guidance: use list_mailboxes to obtain a mailbox id, and explicitly notes the recipient address is not chosen by the caller but read from the lead record. It doesn't explicitly say when to prefer this over send_lead_sms, but the channel verb makes the alternative clear.

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