add_comment

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

Goes well beyond the annotations by disclosing a real side effect not encoded anywhere else — everyone in the thread gets notified — plus the required 'comments:write' scope and a mandatory user-confirmation workflow. This is the actionable behavioral context an agent needs before mutating state.

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 verb, resource and ownership scope before the mode detail and the confirmation warning. Dense and mostly waste-free, though the first sentence is somewhat run-on.

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 4-parameter mutation with no output schema, the description covers purpose, modes, prerequisites and side effects. It stops short of saying what comes back (e.g. the new comment id), which a caller might want but which is minor given the simplicity of the operation.

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 already 100%, so the baseline is 3; the description adds mode semantics the schema does not — timestampMs marks a new comment's pin point while parentCommentId switches the call into reply mode. That framing meaningfully disambiguates how the two optional parameters are used together.

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 ('Post a comment on a recording') plus scope ('the user owns, under the user's name'), and the two modes (new pinned comment vs. reply) frame it clearly against the sibling list_comments, which only reads comments.

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?

Explicitly distinguishes the two invocation modes (timestampMs for a new comment, parentCommentId for a reply) and adds an operational guideline: show the user the exact text and confirm before posting. It never names list_comments as the source of parentCommentId, so alternatives are implied rather than stated.

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