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

The annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds genuine context beyond that: the catalog 'refreshes with the loader capabilities' (dynamic, not static), and ordering is 'first source occurrence rather than a hard-coded list,' which tells the agent results are de-duplicated and order-sensitive.

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 core action, then the handoff to the sibling tool, then the freshness caveat. No filler or repetition of the tool name as a sentence.

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 return values need no explanation, and the description covers what the tool yields, the ordering contract, and where to go next. Only minor gaps remain, such as whether the list is stable across refreshes or approximate size, which is acceptable for a no-parameter discovery tool.

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?

There are zero parameters, so the baseline is 4. The description correctly confirms 'Takes no input,' matching the schema's empty object with additionalProperties=false; there is nothing further to document.

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: 'Discover every loader field name advertised by Modrinth's native loader catalog.' It also explicitly contrasts with a hard-coded list and names the sibling field_values tool, so an agent can distinguish it from modrinth_metadata_loaders and modrinth_metadata_loader_field_values without opening schemas.

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?

'Takes no input; pass a returned name to modrinth_metadata_loader_field_values for its enumerable values' gives a clear use-then-next-step path and names the alternative for downstream lookup. It lacks any when-not guidance, such as when to call modrinth_metadata_loaders instead, so it falls short of a full 5.

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