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 the no-input nature of the call and its position as the first step in a loader/field/value discovery chain. It does not mention rate limits, caching, or remoteness of the Modrinth API, which would be the remaining behavioral gaps for an open-world read tool.

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?

Two sentences, both front-loaded: the capability list comes first, then the navigation hint. No restatement of the name, no filler, and every clause adds either scope or routing information.

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?

An output schema exists, so the return shape need not be explained, and the description instead spends its budget on scope and on the follow-up call chain. For a zero-parameter discovery tool with readOnly and openWorld annotations, nothing an agent needs in order to call it correctly is missing.

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 takes zero parameters, which sets the baseline at 4, and the description confirms 'Takes no input' so there is no ambiguity about passing arguments. Nothing further is needed on this dimension.

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?

Names a specific verb ('List') and a precise resource ('Modrinth's native v3 loader capabilities'), then enumerates the contents: loader name, supported games, supported project types, supported fields and metadata. The closing pointer to modrinth_metadata_loader_fields separates it from the sibling tools that consume field names, so an agent can pick it without opening any 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?

Explicitly states 'Takes no input' and routes the agent forward: use modrinth_metadata_loader_fields to find the field names that modrinth_metadata_loader_field_values accepts. That gives clear workflow context and names two alternatives, but it never states the reverse direction (when this discovery step is unnecessary) or any exclusion, so it falls short of full 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.