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

Annotations only cover the read/write/idempotency/openWorld profile; the description adds what they cannot: required authorization ('editor permission and validation.write'), the ordering prerequisite against list_comments, the reopen-before-reply rule, and guidance to use a stable idempotency key. This is substantive behavioral context beyond structured fields.

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?

Five short imperative sentences, front-loaded with the action and the prerequisite, with no filler. Each clause conveys an operational fact (what, order, precondition, auth, idempotency).

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?

An output schema exists, so return values need not be described, and annotations cover the safety profile. Prerequisites, permissions, and idempotency are covered; the remaining gap is the ambiguous dual project identifiers, which leaves an agent guessing on required input semantics.

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?

With 0% schema description coverage across 5 parameters, the description must carry the load, and it only partly does: it explains that body is plain-text and that idempotency_key should be stable. It leaves thread_id, and crucially the distinction between the two similarly named IDs (project_id vs. validation_project_id), completely unexplained.

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+resource: 'Add a plain-text reply to an open shared discussion.' The word 'reply' distinguishes it from validation.create_comment, and 'Reopen resolved discussions before replying' implicitly contrasts with validation.resolve_comment. It never names those siblings explicitly, so the differentiation is inferential rather than stated.

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 explicit prerequisites ('Read validation.list_comments first', 'Reopen resolved discussions before replying') and names a sibling to call beforehand. It does not state when not to use this tool (e.g. replying to a thread you haven't loaded, or replying to a closed thread vs. reopening it).

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