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

Annotations already declare openWorldHint=false, destructiveHint=false, and idempotentHint=false, so safety and repeat-call behavior are covered structurally. The description adds genuine value with the notification side effect ('Comments notify project collaborators according to their notification preferences'), which is the kind of external consequence annotations can't express. However, it says nothing about permissions, what happens on an invalid anchor, or which anchor shape pairs with which anchorType.

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 tight sentences with no filler; the primary branching logic (reply vs. new thread) is front-loaded and the side effect follows as secondary context. Every clause carries information an agent needs.

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 needn't be explained, and the notification side effect is a nice addition. Still, for a 5-parameter mutation tool with zero schema description coverage, an agent is left guessing about projectUid's role, what 'text' content is expected, and the anchor-shape-to-anchorType mapping — gaps that would likely cause a malformed first call.

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 0%, so the description carries the burden, and it partially discharges it by explaining the threadUid-vs-anchor mutual exclusivity and the anchorType/anchor pairing — semantics the raw schema does not express. But the two required parameters (projectUid, text) get no mention, and the description never maps anchorType 'text_range' to the wordStart/wordEnd variant versus 'generated_video' to the id/version/timestamp variant, leaving the anyOf ambiguous.

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 uses a specific verb-plus-resource framing ('Reply to threadUid, or start a thread') that makes the two operating modes of this tool immediately clear, distinguishing it from siblings like update_comment or delete_comment. It stops short of naming any sibling explicitly, so it lands at 4 rather than 5.

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?

It gives concrete routing logic: supply threadUid to reply to an existing thread, or supply anchorType plus anchor to open a new one. What's missing is negative guidance — nothing says what to do if both are supplied, or that update_comment is the tool for editing an existing comment.

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