Send a direct message

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

Adds substantial behavior beyond the annotations: the 24-hour messaging window, the single-image limit, the one-private-reply-per-comment rule, and the IG_ENABLE_WRITES=true write gate. Annotations only cover the generic readOnly/idempotent/openWorld profile, so the description carries real operational context.

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?

Three tightly packed sentences, front-loaded with the core action and followed by constraints and the alternate mode. No filler or repetition.

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 write tool with no output schema, it covers the key operational constraints (time window, media limit, write flag, private-reply semantics). It omits error/response behavior and does not spell out what happens if both text and image_url are provided.

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 coverage is 75%, and the description adds meaning on top: text and image_url are alternatives ('text or one image'), and recipient_comment_id is framed as an alternative path to recipient_id that triggers a private reply. It doesn't state that no parameters are required or clarify failure when neither text nor image is supplied.

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+resource ('Sends a DM') and enumerates the two supported payloads (text or one image), plus a distinct private-reply mode. It does not name a sibling tool, so differentiation from ig_reply_comment and ig_get_messages is only implicit.

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?

Gives concrete usage conditions: only within 24 hours of the recipient's last message, one image maximum, and recipient_comment_id for private replies (one per comment). It never explicitly says when to prefer a different sibling tool, but the routing between the two modes is clear.

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