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

Annotations already cover readOnlyHint=false, destructiveHint=false, idempotentHint=true. The description adds genuinely useful behavioral context: the caller must have comment access and creation is rate-limited. It clarifies that the thread is open and anchored to an immutable version. This goes beyond annotations without contradicting them.

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?

The description is only two sentences, with the core purpose front-loaded in the first sentence and usage guidance in the second. Every phrase earns its place—no fluff, no redundancy with schema.

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?

Given the tool's moderate complexity, the description covers purpose, usage context, permissions, and rate limits. The schema and annotations handle parameter details and safety semantics, and an output schema is present, so no return-value explanation is needed. It feels complete for an agent to select and call correctly.

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 100% with descriptive parameter details, so the baseline is 3. The description's mention of anchoring options (whole artifact, exact text, HTML element) summarizes what the schema already documents in detail via const values and descriptions. It does not add new semantic meaning beyond the schema.

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 clearly states a specific verb and resource: 'Create a new open review thread with its first comment', and specifies anchoring options (whole artifact, exact text, HTML element) and immutable version. It distinguishes itself from the sibling tool reply_to_thread by explicitly directing existing discussions there.

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 explicit guidance: use for creating a new thread, and 'Use reply_to_thread for an existing discussion instead' names the alternative. It also adds context about caller permissions ('needs comment access') and rate limiting, helping the agent decide when to invoke.

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