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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false, indicating a mutating, non-idempotent operation. The description's 'Edit' aligns with this but adds no new behavioral detail beyond the prerequisite of chat-list. It doesn't clarify what happens when both content and flavor are provided (likely both are updated), but that's not a major gap given the schema covers the parameters.

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 concise (two sentences) and front-loaded with the purpose. Every sentence earns its place: it states the action, gives concrete use cases, provides a necessary prerequisite, and states a key constraint. No fluff or redundancy.

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 update tool with three parameters (one required) and no output schema, the description covers the essentials: what it does, how to obtain the required ID, and a usage constraint. It doesn't mention the return value or error behavior, but these are not critical for a basic mutation. It could clarify that both fields can be updated simultaneously, but that's a minor omission.

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%, so all three parameters are documented. The description adds value by specifying that at least one of content or flavor must be provided—a constraint not enforced by the schema (only messageId is required). It also points to chat-list as the source for messageId, which is useful. This exceeds the baseline 3 for full coverage.

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 tool's purpose: 'Edit content or flavor of an existing chat message.' It distinguishes from siblings like chat-send (creating new messages) and chat-delete (removing), and even gives specific use cases ('fix typos in DM narration or update descriptions'), making it easy for an agent to know when this tool applies.

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?

It gives a clear prerequisite: 'Use chat-list FIRST to find the message ID.' It also states a necessary constraint: 'At least one of content or flavor must be provided.' However, it does not explicitly mention when NOT to use it (e.g., for new messages use chat-send), though this is implied by the sibling names and context.

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