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

No annotations are provided, so the description carries the full burden, and it delivers: attribution is to the caller's own grant (no impersonation), and it explains pinning targets. It does not state mutation/irreversibility or whether edits are later possible, but covers the key identity constraint well.

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?

Two sentences, front-loaded with the core action (reply or new thread), then anchoring. Every clause earns its place with no filler.

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?

Given 9 params, no annotations, and an output schema present (so return values need not be explained), the description covers action, targeting, and attribution. It leaves x/y frame-fraction ambiguity partly to the schema, but the composition is otherwise complete for correct invocation.

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 78%, so the schema documents most params; the description adds real semantic value beyond it by explaining the reply-vs-new-thread distinction for threadId, the three mutually-alternative anchor mechanisms, and the frame-fraction convention for x/y. Only body, designId, and token are not elaborated in prose.

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?

States a specific verb (post/say something) and resource (comment on a design), and distinguishes the reply-vs-new-thread behavior from siblings like ui_builder_list_comments and ui_builder_react_to_comment. The anchor semantics (markId/nodeId/x/y) make the tool's purpose unmistakable.

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?

Explains the two primary modes — reply via threadId, or new thread when omitted — with clear conditions. However, it doesn't contrast with adjacent siblings such as react_to_comment or acknowledge_comment, so the agent has no explicit guidance on why this tool over those.

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