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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the safety profile is covered. The description adds one genuinely useful behavioral note — that these reference choices do not restrict the native expression grammar — which prevents an agent from assuming the listed values are a closed enum. Beyond that it doesn't mention auth, rate limits, or whether the vocabularies change over time.

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 lead clause is well front-loaded, but the rest is a single dense sentence with heavy noun-stacking ("exact native content and status filter expressions, all disclosure-search flags"). The list of vocabularies would read far better as an enumerated structure, and terms like "disclosure-search flags" are unexplained jargon.

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 an output schema present and no parameters, the description's job is mainly to set expectations about scope, which it does by listing the vocabulary families. The only gap is that it doesn't tell the agent how to consume the result in relation to the sibling search tools.

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?

The tool has zero parameters, so the baseline is 4. The description explicitly confirms "Takes no input," which is consistent with the empty schema and removes any ambiguity about whether filters can be passed here.

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 gives a specific verb and resource ("Discover the Modrinth v3 search vocabularies") and enumerates the concrete vocabularies returned: indices, server regions, languages, content/status filter expressions, disclosure-search flags, and discovery paths for project types, categories, loaders, game versions, environments and licenses. This makes it distinguishable from the similarly named modrinth_search_v3, which is the actual search. It is not named-differentiated explicitly, but the content list is specific enough that an agent can tell what it returns.

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?

Usage is implied rather than stated: an agent can infer this is a reference/lookup call to make before constructing a search. However, the description never says when to call it versus modrinth_search_v3 or modrinth_search_v3_body, nor does it say whether it should be cached or called repeatedly. "Takes no input" is the only operational hint.

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