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

Annotations already declare the mutation profile (destructive, idempotent, open-world), yet the description adds real value: PUBLIC visibility, the write:content scope requirement, surface-specific limits (500 vs 4,000 code points), and the fact that retries with the same key return the original result. It stops short of noting failure modes or what happens if the thread is locked/archived.

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?

Information-dense and front-loaded: visibility, parent behavior, limits, scope, and return value in five tight sentences. The agent-guide URL is the only element of marginal value, but it is short.

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 6-param mutation tool with no output schema, the description covers what matters: required scope, visibility, size limits, return shape ('permanent reply address'), and idempotency. The only gap is the undiscussed 'watch' parameter and any error conditions.

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 only 33%, so the description must compensate. It does explain parent_id's root-selection behavior and re-states the idempotency_key contract, and its length limits add nuance beyond the schema's 16384 maxLength. However, 'watch' is never explained, and body/thread_id semantics are left to the schema's type definitions.

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 ('Publish a PUBLIC reply in an existing thread') and the visibility qualifier immediately distinguishes it from a private-message or thread-creation tool like create_thread. An agent can tell what this does without opening the schema.

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 implies the precondition of an existing thread ('in an existing thread') but never explicitly routes the agent to siblings (e.g., 'use create_thread to start a new thread'). The parent_id rule and per-surface length limits are useful behavioral facts but are not when/when-not guidance.

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