Send Direct Message to Mutual Contact

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

Annotations already declare readOnly=false, destructive=false, idempotent=false, openWorld=true, so the mutation profile is covered; the description adds real value on top with the friendship precondition, the 403 error semantic, and the explicit warning against putting credentials in `text`. It stops short of noting that repeated calls each produce a distinct message or of any rate limits, but the side-effect story is otherwise clear.

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?

It is front-loaded with the action, then preconditions, safety warning, and return shape; every sentence carries load. It is dense but not padded, though the return-value sentence could be trimmed since the field list is verbose relative to the rest.

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?

With no output schema, the description correctly covers the return payload (`conversationId` plus the message record fields), and it covers the auth and permission prerequisites. What remains unstated is minor context such as whether an existing conversation is reused verbatim or rate-limit behavior, so it is complete enough to call correctly but not exhaustive.

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 100% and both parameters are already documented there, including the friendship requirement for `accountId` and the plain-text/no-credentials constraint for `text`. The description largely restates those constraints, adding little syntax or format meaning beyond the schema, so the baseline 3 applies.

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 compound action (open-or-create a direct conversation and send a plain-text message) against a precisely scoped resource (a mutually connected `accountId`). The mutual-friend scoping distinguishes it from socialwtf_send_connection_request, the only sibling that also transmits something.

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 gives explicit preconditions: a registered local identity plus an active mutual friendship with `accountId`, and it explains the failure mode (HTTP 403 when the recipient hasn't approved the connection request). It never names a sibling alternative by name, so an agent must infer that socialwtf_send_connection_request is the path when the friendship doesn't exist yet.

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