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

Annotations give destructiveHint=true, and the description adds value beyond that: it explains the identity/permission constraint on who may edit and warns that the change is delivered immediately. It does not cover reversibility or error behavior, so it is strong but not exhaustive.

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 tight sentences, front-loaded with purpose and followed by the two constraints an agent most needs. No filler, though the composite-id note is somewhat redundant with the schema.

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 mutation tool with no output schema, the description covers the key concerns: what changes (text is replaced), who can do it, and the immediacy risk. Sufficient to call correctly, with minor gaps around failure modes.

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 parameters are already documented, and the description's note about `channel` accepting a composite 'channel:ts' largely restates the schema's own wording. Baseline 3 applies.

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 ('Rewrite a Slack message's text') with the underlying API ('chat.update') named, and it is clearly distinguishable from siblings like delete_slack_message, send_message, and update_draft.

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?

States a real prerequisite (only the original poster's identity can edit) and an operational caveat (confirm new text with the user because the edit delivers immediately). No explicit sibling alternative is named, but the context needed to decide when to call it is present.

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