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

Annotations already cover read-only/idempotent/open-world, but the description adds real behavior: no caching, a live Modrinth call per invocation, potential failure when Modrinth is down with a retry hint, resolution by jar SHA-1 then slug, and found:false rather than an error for unknown mods. This is far beyond the annotation set.

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?

One dense paragraph that is front-loaded with purpose, then usage, then resolution/failure semantics; nearly every clause carries information. It is long for a single-parameter tool, and the resolution detail could be tightened, but nothing is filler.

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, return-value detail is unnecessary, and the description still covers prerequisites, resolution order, the found:false non-error case, and the live-call failure mode. Nothing needed to invoke 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?

Schema coverage is 100%, so the baseline is 3, but the description adds meaning: the value may be a lab mod id or a Modrinth slug, is matched by jar hash then slug, and a plain name requires search_mods first. That is more than the schema's format hint.

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 concrete verb and resource (fetch a mod's Modrinth catalog page plus a Modkeel lab record) and enumerates the fields returned, so an agent knows exactly what it gets. It explicitly separates itself from siblings get_mod_runs, check_mod_pair and search_mods.

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?

Gives explicit trigger questions ("what does this mod do?", "is it client-only?", "where do I download it?"), names the alternatives for adjacent needs (get_mod_runs for observed behavior, check_mod_pair for two mods together), and states the prerequisite of calling search_mods when only a name is known.

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