Pin comment

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

Goes beyond the annotations (readOnlyHint=false, idempotentHint=true, destructiveHint=false) with facts the annotation block cannot express: the permission requirement (admins/moderators), that it sends no notification to anyone, and that it is undone with one call. It even resolves the practical question of whether to prompt the user for confirmation, which is exactly the kind of context an agent needs for a mutation.

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, front-loaded with the action and its inverse, with the permission and safety notes following. There is mild redundancy between 'Pin a comment to the top' and 'Pins one comment above the others', but no filler otherwise.

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 four-parameter toggle with full schema coverage and annotations, the description covers the essentials: what it does, the inverse operation, who may call it, side effects, and reversibility. It never indicates what the call returns, which is a minor gap given there is no output schema, but nothing needed to invoke it correctly is missing.

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 description coverage is 100%, so all four parameters are already documented, including the pinned-false-unpins semantics. The description restates the unpin behavior but adds no format, default, or sourcing detail beyond what the schema provides, so the baseline of 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?

States a specific verb and resource ('Pin a comment to the top of a post's comments, or unpin it') and the second sentence clarifies the scope as one comment above the others under a post. This is clearly distinct from the sibling pin_post, which operates on posts rather than 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?

Gives a clear condition for invocation (group admins and moderators only) and an explicit operational directive that it 'runs without asking first' because it is silent and reversible. It does not name an alternative sibling or state when not to use it, but the toggle semantics ('pinned false unpins it') make the when-to-use obvious.

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