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

Annotations already declare readOnly=false, destructive=false, openWorld=true; the description adds real context beyond them — the open-thread precondition and an explicit prompt-injection warning about untrusted comment bodies. It stops short of saying what a successful reply returns or whether notifications/mentions trigger side effects.

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 short sentences, each earning its place: action, precondition, and safety note, with the core action front-loaded. No filler or restatement of the name/title.

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 non-idempotent, open-world mutation with no output schema, the description covers the key behavioral risks (closed threads, untrusted content). It omits return/confirmation behavior and any permission requirements, which are the remaining gaps.

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 67%: body and id are well documented in the schema, threadId is not. The description adds semantic meaning for body ('user-written content, possibly from people outside the workspace') but says nothing about threadId or how to confirm the target thread. Roughly baseline for this coverage level.

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 and resource ('Reply to an open comment thread') plus the acting identity ('as the signed-in user'), which separates it from create_comment_thread. It never names resolve_comment_thread or get_comment_thread explicitly, so sibling differentiation is only implicit.

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 a clear precondition/exclusion: 'Resolved threads must be re-opened first,' which tells the agent when this tool will fail and implies the prerequisite action. It does not name the re-open or resolution tool to use instead, so the routing is left to inference.

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