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

Annotations already indicate this is a write operation (readOnlyHint=false) and not destructive. The description adds useful behavioral context: @mention parsing is automatic, and replies must reference the root comment. These details go beyond the annotation flags, giving the agent a better mental model of tool behavior.

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 primary purpose and zero filler. Every clause adds value: required body, automatic @mention parsing, and reply semantics. High signal-to-noise ratio.

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 an 8-parameter mutation tool with no output schema, the description covers the core behavior but omits critical context such as the meaning of `id` (presumably the post ID) and the role of `idempotency_key`. The schema's workspace description covers the workspace requirement, but overall the agent would need to make assumptions about several parameters.

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 about 63% (5 of 8 parameters have descriptions). The description reinforces that `text` is required and @mentions are automatic, but that is already in the schema. It adds a meaningful constraint for `parent_comment_id` (must point to the root comment). However, required fields like `idempotency_key` and `id` remain unexplained in both schema and description, leaving a gap.

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 begins with a specific verb+resource: 'Create a comment on a post.' This clearly distinguishes it from sibling tools like create_post (creates a post itself) and update_post_comment (modifies an existing comment). The additional details about @mentions and replies further clarify the scope.

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?

The description provides clear context: text body is required and replies need parent_comment_id pointing to the root comment. This offers practical usage guidance for the main scenarios. However, it does not explicitly mention alternative tools for editing or deleting comments, so it falls short of a perfect score.

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