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

Annotations already declare readOnly, idempotent, non-destructive, so the safety profile is covered. The description earns credit beyond that by disclosing data provenance: these are self-reported distinct owners, not verified installations, and an install can succeed while the mod is untested. That is exactly the kind of caveat an agent needs to avoid over-claiming reliability.

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?

Three short sentences, front-loaded with the definition of what is counted, followed by two caveats. Every sentence carries information, though the third ("functionality remains untested") overlaps the second's point that these are unverified user reports.

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 one trivially documented parameter and annotations covering safety, the only real gap is output shape: there is no output schema, and "counts" (plural) does not reveal whether the response is a single number, per-version breakdown, or per-platform split. An agent cannot anticipate the return value from this description.

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 single modId parameter is documented in the schema as "a catalog mod slug or mod: ID." The description adds no format, lookup, or error semantics beyond that, so 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?

"Public distinct-owner counts for a catalog mod" names the exact resource (a mod) and the exact metric (distinct-owner report counts), and the word "public" implicitly distinguishes it from get_my_installations. It stops short of naming which sibling to use instead (get_mod, get_top_mods), so it is clear but not fully differentiated.

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 never says when to call this versus get_mod, get_top_mods, or get_my_installations, nor does it state any precondition beyond supplying a mod ID. The disqualifiers it does give are about interpreting the numbers, not about tool selection.

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