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

Annotations already declare readOnly/idempotent/non-destructive, so the description doesn't need to cover safety. It adds non-obvious behavior instead: the browser UI exposes human-readable labels while the API requires internal names, and one cannot be derived from the other. It does not mention ordering or what happens when no track matches.

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-style questions an agent will encounter, then the capability statement, then the downstream-routing rationale. It is a single dense paragraph — the parenthetical example and the label/name contrast both earn their place, but the block is longer than it needs to be.

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, and the description compensates by enumerating the per-track fields returned. Genome-choice risk is handled thoroughly in the schema, so it needn't repeat that. It stops short of saying how results are ordered or whether the list is truncated beyond `limit`.

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. The description earns a step above by clarifying the name/label duality, which explains why `search` matches across track name, short label and long label, and why results carry both identifiers.

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 (lists annotation tracks available on one UCSC assembly) plus the fields returned (internal name, short/long label, data type, parent container). The distinction from ucsc_track_data is made explicit: this is the lookup used to obtain a valid track name for that tool.

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?

Three quoted trigger phrasings define when to reach for it, and the sentence 'AUTHORITATIVE for the `track` argument of ucsc_track_data' names the sibling and the exact condition that routes the agent here first. A concrete worked example (label "GENCODE V50" maps to track `knownGene`) shows why guessing is unsafe.

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