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

No annotations are provided, so the description carries the full behavioral burden. It does not disclose whether the send can be undone, what permissions are required, whether rate limits apply, or what the result looks like; for a mutation tool this is a substantial gap.

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 with no wasted text. It prioritizes the action and the prerequisite dependency clearly.

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 messaging mutation tool with no annotations, no output schema, and no explicit error or permission behavior, the description is too thin. The schema covers parameters, but the description leaves important behavioral context unstated.

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%, so both parameters are already documented in the schema. The description only adds the recipient-resolution dependency and does not elaborate on the body text or notification_message semantics, making the baseline 3 appropriate.

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 Direct text message') and identifies the recipient resolution dependency. It is clear enough to distinguish from siblings like direct_thread or direct_inbox, though it does not explicitly contrast those alternatives.

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 phrase 'the user resolved in resolve_recipient' implies a necessary prerequisite step, which is useful usage context. However, it gives no explicit when-not guidance, no alternatives for different DM operations, and no error or fallback conditions.

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