send_dm

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

With no annotations, the description carries the transparency burden. It discloses that the message is private and that bulk calls risk account suspension, adding important behavioral context beyond what the schema provides. It doesn't cover all failure modes but does provide meaningful risk information.

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 brief and front-loaded, with a clear purpose statement followed by a risk warning and an Args list. Every sentence adds value, and the structure is easy to parse.

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?

Given the simple 3-parameter tool and the presence of an output schema, the description covers the core purpose, parameter semantics, and key risk warning. It lacks explicit when-to-use vs alternatives, but combined with schema and output schema it is sufficient for invocation.

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?

The description adds crucial semantics beyond the bare schema: it specifies that screen_name should be without '@', that text must be non-empty, and that media_id is optional. Since schema description coverage is 0%, this fully compensates for the schema's lack of parameter explanations.

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 opens with a clear action verb ('Send') and identifies the specific resource ('a direct message to a user by screen name'). This distinguishes it from siblings like send_tweet and send_dm_to_group.

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 context that DMs are private and warns against bulk-calling due to X's aggressive anti-spam, which helps an agent decide when to invoke this tool sparingly. It doesn't explicitly name alternatives, but the screen-name targeting implies one-on-one DMs, distinguishing it from send_dm_to_group.

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