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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior. The description adds context that the output is 'compact' and 'source-pinned', which goes beyond annotations. No contradictions. However, 'source-pinned' is somewhat vague, so it doesn't fully explain the output's nature.

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 a single, well-structured sentence that front-loads the primary usage condition and then lists alternatives in a clear sequence. Every part contributes value with no redundancy.

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?

The tool is simple (one parameter, no output schema, read-only, idempotent). The description explains when to use it and what it provides, but it doesn't specify the exact output format or contents of the 'handoff.' Given the low complexity, it is largely complete, though a bit more detail on the output would make it fully self-sufficient.

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 100%, and the only parameter (thread_id) is already described as 'Target public thread UUID.' The description adds no additional semantics for the parameter, so a baseline score of 3 is appropriate.

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 states a clear purpose: providing a compact, source-pinned handoff for continuing work on a known thread. It distinguishes itself from siblings by naming alternatives, but it lacks a crisp verb+resource structure (e.g., 'returns a summary'). The intent is clear, though slightly usage-oriented rather than a direct definition.

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?

Explicitly provides when to use this tool and when to prefer alternatives: 'Prefer commons_read_thread when you need the thread itself, commons_resume for changes since a stored event cursor, and commons_snapshot for a broader current-state overview.' This fully satisfies the dimension.

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