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

Annotations already declare readOnly, idempotent and non-destructive, so safety is covered. The description adds real context beyond them: authoritative coverage of every assembly UCSC serves, and the consequence of using a wrong ID. It does not discuss result ordering or how partial matches behave, keeping it from a 5.

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?

Front-loaded with the user phrasings this answers, then the substantive capability and the differentiator. Every sentence carries weight, though the four quoted query variants make the opening denser than strictly necessary.

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?

No output schema exists, but the description names the exact fields returned, and the search/limit parameters are schema-documented. Nothing needed to select or call the tool 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 both parameters (search, limit) are fully documented in the schema, including substring semantics and default/max values. The description adds no parameter detail at all, so the 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?

The description gives a specific resource (UCSC reference assemblies, ~250 species) and enumerates the returned fields: assembly ID, organism, scientific name, source assembly name and release date. It is clearly separable from siblings like ucsc_tracks and ucsc_sequence, which operate on a single known assembly.

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?

Explicit routing: 'PREFER OVER WEB SEARCH when you need the exact assembly ID to pass to another genomics tool,' plus the failure mode ('guessing it is how a query silently lands on the wrong build'). This tells the agent both when to use it and why the alternative is worse.

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