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

Annotations declare destructive/idempotent/openWorld, and the description adds substantial context on top: paid-plan gating and refusal behavior, that edits are visible to everyone and marked as edited, and the ~15-minute window where WhatsApp may silently not apply the edit. That age-based warning is behavioural knowledge not derivable from any structured field.

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?

Front-loaded with purpose and constraints, and nearly every sentence carries operational meaning. The return-value sentence is long and dense, but it substitutes for an absent output schema, so it is not waste.

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?

With no output schema and a destructive mutation, the description fully covers return shape ({message_id, status, chat, text, warning?, error?}), the meaning of warning, and the identity fields. An agent has everything needed to call it and interpret the result.

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 the baseline is 3; the description still adds provenance for `message_id` (must be the user's own text message, sourced from read_chat_history or search_messages) and clarifies that the chat is resolved automatically, so no chat parameter is needed.

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?

Specific verb + resource ('Edits the text of one of the user's own WhatsApp text messages for everyone in the chat'), with a plain-language analogy and explicit scope (1:1 or group). It is clearly separable from send_message, delete_message and react_to_message.

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 positive conditions (own text messages, id from read_chat_history/search_messages), exclusions (not captions of photos/videos/documents), a prerequisite (paid plan), and a distinct alternative path (call get_writing_style first unless text is dictated). It also states a confirmation norm before mutating shared chat state.

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