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

Annotations already declare the write/idempotent/non-destructive profile. The description adds behavior beyond them: the message is private (visibility), and it explicitly disclaims triggering a booking or a guaranteed reply, which sets correct agent expectations. It does not detail auth requirements, which the schema partially carries.

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?

Two short sentences, front-loaded with the action and privacy constraint, followed by an expectation-management clause. No filler; every clause 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?

There is no output schema and the schema covers most parameters, so the description's job is mostly behavioral. It conveys privacy and outcome expectations but omits the auth/posting-key requirement, which is left to the schema. Adequate but not exhaustive for a write operation.

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 75%, with accessKey, reference, and requestId already documented (including retry semantics). The description adds no parameter-level meaning, so it neither compensates for the uncovered 'message' param nor improves on the schema. Baseline 3 fits since the schema does the heavy lifting.

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 (send a private text message) and emphasizes PRIVATE, which implicitly distinguishes it from the sibling post_message. It does not explicitly name the sibling it contrasts with, but the scope is clear enough to select it correctly.

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 implies usage context by specifying 'in your existing proposal room' and clarifies what the tool does not do ('does not book a meeting or promise an immediate reply'). However, it never states when to prefer this over post_message or read_conversation, so the routing guidance is only implied.

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