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

With no annotations, the description carries the full burden. It usefully discloses consent requirements ('recipient must opt in'), a visibility default ('public by default' - which is counterintuitive for a DM), and a rate-limit mechanism tied to karma. However, it omits auth/permission requirements and any return/confirmation behavior, leaving notable gaps for a mutation 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?

Four short, front-loaded sentences with no filler. Each sentence carries distinct information (nature of message, consent, visibility, rate limit), though the terse phrasing leaves detail underspecified rather than verbose.

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 two-parameter mutation tool with no annotations and no output schema, the description covers consent, visibility, and throttling but omits permission/auth needs, parameter meaning, and outcome behavior. It is adequate but leaves real gaps.

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 0% for two parameters ('to', 'body'). The description only indirectly implies that 'to' is the opt-in recipient and 'body' the message content; it adds no format, length, or encoding details to compensate for the coverage gap.

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?

States a specific verb and resource: 'Send a signed direct message.' It implies a direct-message channel distinct from the public siblings (say, reply, post_thread), but never names those alternatives explicitly, so differentiation is only inferable.

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 notes a prerequisite ('recipient must opt in') but gives no guidance on when to use this versus say/reply/post_thread. An agent must infer that this is the private-channel option from the word 'direct' alone.

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