Send Private Message

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

Annotations already cover mutating, non-idempotent, non-read-only behavior, so the description's addition of the 'logged-in web session' requirement adds useful behavioral context. It does not contradict annotations and gives a prerequisite that an agent must know before invoking the tool.

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 a single, front-loaded sentence that states the core action and a key prerequisite. There is no wasted wording, and it is easy to scan.

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 mutation tool with no output schema and several parameters, the description is too minimal. It omits any mention of what happens after sending, expected return values, or specifics about the optional parameters (html, dry_run). The session requirement is the only added context, leaving many operational details unaddressed.

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 60% (to, text, dry_run have descriptions; title and html do not). The description adds no parameter-specific details, failing to compensate for the undocumented title and html parameters. An agent must infer their meaning from names alone, which is insufficient.

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 clearly states the action: 'Start a new private conversation' with one or more members, and distinguishes it from reply operations by using 'new'. The title also clarifies the resource. This differentiates it from pm_reply and other siblings without requiring schema inspection.

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 provides clear context by specifying 'new private conversation' and the forum messenger compose context, which implies it is for initiating rather than replying. However, it does not explicitly name alternatives like pm_reply or state when not to use it, so it lacks explicit exclusion guidance.

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