send_message

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

Discloses end-to-end encryption, return value (timestamp) for reactions/edits, and quoting behavior. No annotations provided, but description adds useful behavioral context beyond schema.

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 concise sentences, front-loaded with purpose and encryption, then return value and usage tips, then alternatives. No unnecessary words.

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 simple parameter set with full schema coverage and no output schema, the description covers purpose, usage, return value, and relationship to siblings. Adequate for effective agent 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?

Schema coverage is 100% so baseline is 3. Description adds value by explaining the usage of quote_author and quote_timestamp (for quoting) and the return timestamp usage.

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 verb 'Send' and resource 'text message to a Signal contact', and distinguishes from siblings by mentioning send_group_message and send_attachment for 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?

Explicitly states when to use this tool vs alternatives: for group chats use send_group_message, for attachments use send_attachment. Also explains how to reply/quote using quote parameters.

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