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

Annotations only declare the generic profile (readOnly=false, destructive=false, openWorld=false), so the description usefully adds that the reply is "visible to everyone with access to the file" and that the server appends an "employee and agent" signature. These are non-obvious side effects that shape whether an agent should post. It does not say what the call returns or how failures surface.

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 compact clauses, front-loaded with the action and visibility, then sourcing, then the suitability rule. Every sentence carries information, though the sourcing clause reads as telegraphic shorthand.

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, it covers visibility, the signature side effect, language/length expectations and when to refrain. The main gap is return behavior (e.g., the new reply's ID) and error handling, which an agent posting into a shared thread might want.

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, but the description adds real semantics: "Source: url or designID" clarifies these two are alternative locators for the same thing, and commentID may be "the thread or a reply in it". That resolves ambiguity the schema alone leaves open.

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 opens with a specific verb and resource ("Replies in a Figma comment thread") and scopes the channel ("through the company's integration"). It is clear what the tool does, but it never names or contrasts with the obvious sibling design_comments, so an agent must infer the read-vs-write split itself.

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 an explicit positive condition ("Suitable when a remark is fixed or the answer is unambiguous") and a negative one ("disputed points are left to the user"), which is real routing guidance. It stops short of naming an alternative tool to use for the disputed case, so it is clear context rather than a full when/when-not/alternative map.

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