send_message

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

With no annotations, the description carries full burden. It discloses key behavioral traits: it's a mutation tool (implied by 'send'), has a failure condition ('Will fail if recipient is not in the allowed list'), and hints at auth/access control. However, it lacks details on rate limits, response format, or error handling, leaving gaps for a tool with no annotations.

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?

Two sentences, zero waste. First sentence states purpose and scope, second sentence adds critical behavioral constraint. Every word earns its place, and information is front-loaded appropriately.

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 and no output schema, the description is moderately complete. It covers the core action and a key constraint, but lacks details on return values, error types, or side effects. For a mutation tool with 2 parameters, this is adequate but has clear gaps, scoring a minimum viable 3.

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%, with both parameters well-documented in the schema. The description adds no additional parameter semantics beyond what's in the schema (e.g., no extra format details or examples). Baseline 3 is appropriate as the schema does the heavy lifting.

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 'WhatsApp message', specifying the target as 'an ALLOWED phone number or group'. It distinguishes from siblings like 'get_messages' (read) and 'delete_message' (delete), though not explicitly named. However, it doesn't fully differentiate from hypothetical similar send tools, keeping it at 4 rather than 5.

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 clear context for when to use: 'to an ALLOWED phone number or group'. It implies an alternative (check allowed list first via 'list_allowed') but doesn't explicitly name it or state when not to use. No misleading guidance is present, making it a solid 4.

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