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

Annotations already indicate readOnlyHint=false and destructiveHint=false. The description adds valuable behavioral context: that this is a side-effectful email send, the email lookup fallback to WP, and the return shape { sent, to (masked), client_phone }. This goes beyond what annotations provide.

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 compact sentences, front-loaded with the main purpose, followed by conditional usage, return value, and audience. No wasted words; each sentence earns its place.

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?

The description is complete for a moderate-complexity tool with 6 params and no output schema. It explains the action, the email fallback, the return format, and the intended voice-agent context. It relies on schema for individual param details, which is acceptable.

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 each parameter has a description. The tool description adds meaning especially for `email`, explaining when to supply it and when it is auto-looked-up. It also clarifies that `driver_first_name` should be first name only (echoed from schema). This is useful beyond the schema.

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 explicitly states 'Email the booking's client their assigned driver's first name + phone', which is a specific verb+resource+scope. It distinguishes this tool from sibling tools (none of which send emails) and adds a clear use-case note ('Voice agent use').

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 provides clear conditional guidance: pass `email` if you already have the client's address (e.g., from Zeplan get-booking), otherwise WP looks it up on the booking post. It doesn't explicitly state when not to use the tool, but the context and sibling list make the usage scenario clear.

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