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

Annotations already declare readOnlyHint=false and openWorldHint=true, so the agent knows this is a mutating, side-effectful action. The description adds valuable context by emphasizing 'this delivers a real message', which reinforces the non-idempotent, real-world impact and the importance of the confirmation gate. This goes beyond the annotations without contradicting them.

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 three short sentences with zero filler. It front-loads the core purpose, then adds the side-effect and the critical usage condition. Every sentence earns its place and the message is delivered in under 30 words, making it efficient for an agent to parse quickly.

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 action tool with no output schema, the description covers everything an agent needs: what it does, the side effect, and the explicit precondition. The parameters are fully documented in the schema, and the description correctly highlights the one decision-relevant context (the confirmation requirement) that isn't in the schema. 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?

The input schema provides descriptions for all 5 parameters (100% coverage), so the schema already documents each field clearly. The description adds little extra parameter-level meaning: it mentions 'the brief' being relayed, which is already clear from the schema. With full schema coverage, a baseline of 3 is appropriate, and the description does not substantially enhance parameter understanding.

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 ('Book') and a distinct resource ('a project intro with Ruben'), and it further clarifies the action by stating it relays the brief to his email. This clearly differentiates it from siblings like check_availability, get_resume, and get_services, which are about checking or retrieving information rather than initiating an action.

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 gives an explicit condition for use: 'Only call after the person you act for has explicitly confirmed', effectively telling the agent when to use it and when not to (before confirmation). It does not name sibling tools as alternatives, but the purpose statement is explicit enough that an agent can infer get_resume/get_services/check_availability are not the same kind of action.

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