Get one WhatsApp message in full

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

Annotations already carry the full safety profile (readOnlyHint=true, openWorldHint=true, idempotentHint=true, destructiveHint=false), so the bar for added disclosure is lower. The description contributes return-content context (quoted message, reactions, media metadata) beyond annotations but says nothing about failure behavior, authorization, or chat-scoping constraints. This is adequate given the strong annotation coverage.

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?

A single well-structured sentence that front-loads the core function, then enumerates content scope, then routes usage to sibling tools. Every clause earns its place; there is no filler or repetition of title content.

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 single-parameter read-only retrieval tool with fully documented schema and rich annotations, the description explains what the return payload contains (quoted message, reactions, media metadata) even in the absence of an output schema. The usage context is explicit. Only minor gaps like invalid-ID behavior or chat scope remain, but nothing essential to invoking it correctly is missing.

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% — the message_id parameter is fully documented with type, minLength, and a concrete example ('false_4072...@s.whatsapp.net_3EB0...'). The description adds no parameter detail beyond what the schema provides, so the baseline 3 for high coverage is appropriate.

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 uses a specific retrieval verb anchored to a concrete resource ('The complete message behind a message_id') and enumerates exactly what's included: the quoted message, reactions, and media metadata. It clearly differentiates from siblings by framing this as the deep-dive tool that follows search_messages/read_messages, so an agent can distinguish it without opening schemas.

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?

Explicit guidance — 'Use it after search_messages or read_messages when you need the context around a single message' — names the preceding tools and the exact condition that selects this tool. It lacks an explicit when-not-to-use statement, but the conditional phrasing makes the intended workflow unambiguous.

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