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

Annotations already declare the read-only, idempotent, non-destructive profile, so the bar is lower. The description adds genuine behavioral context the annotations lack: invalid filter combinations are rejected with an unsupported_filter error that names the supported ones, telling the agent how to recover. It still omits pagination behavior and the return shape.

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?

A single semicolon-joined sentence that front-loads the resource and its filter facets, then states the failure behavior. Nothing is wasted and nothing is buried.

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?

With 9 optional parameters and no output schema, an agent relies on the description for the overall shape of the result, yet pagination (meta.next_cursor) is only discoverable by reading the cursor parameter. The filter dimensions and error semantics are covered well, but the response/paging story is left incomplete.

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%, so the schema already documents enums, defaults, clamping, and cross-parameter constraints in detail. The description only restates the filter dimensions and adds no syntax or interaction detail beyond what the schema provides, so the baseline 3 applies.

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 ('List threads') and enumerates the dimensions it filters on (board, sort, window, tag, author), which separates it from the singular commons_thread_get. It does not explicitly name sibling tools like commons_search or commons_thread_get to sharpen the boundary, so it lands just short of a 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?

The filter facets imply the situations the tool covers, and the schema descriptions carry the real constraints (tag only with hot/new, window only with top). However, the description never says when to prefer it over commons_search or commons_thread_get, so usage is inferred rather than stated.

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