send_direct_message

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

No annotations are provided, so the description carries full burden. It mentions 'max 1000 characters' for text and 'prevent duplicate sends' for source_guid, adding some behavioral context. However, it lacks critical details: whether this requires specific permissions, rate limits, error conditions (e.g., invalid recipient), or what happens on success (e.g., message ID returned). For a mutation tool with zero annotation coverage, this is insufficient.

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 front-loaded with the core purpose in the first sentence, followed by a bullet-like 'Args:' section that efficiently explains parameters. Every sentence adds value without repetition or fluff. The structure is clear and 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 no annotations, no output schema, and 4 parameters, the description is moderately complete. It covers the purpose and parameters well but lacks behavioral transparency (e.g., error handling, return values). For a mutation tool that sends messages, more context on outcomes and constraints would be beneficial, though the parameter semantics help compensate.

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%, so the description must compensate. It adds meaningful semantics for all parameters: recipient_id ('user ID of the recipient'), text ('message text' with max length), source_guid ('unique ID to prevent duplicate sends'), and attachments ('optional list of attachment objects'). This goes beyond the schema's basic types, though it doesn't fully detail attachment object structure.

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 clearly states the specific action ('send a direct message') and the target ('to another user'), distinguishing it from sibling tools like 'send_message' (which might be for group chats) and 'post_as_bot'. It uses a precise verb+resource combination that leaves no ambiguity about its function.

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 implies usage for direct messaging, but doesn't explicitly state when to use this vs. alternatives like 'send_message' or 'post_as_bot'. It provides no guidance on prerequisites (e.g., recipient must be a valid user) or exclusions (e.g., cannot send to blocked users). The context is clear but lacks explicit comparison to siblings.

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