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

Annotations already mark the operation read-only and idempotent, and the description adds significant behavioral detail beyond that: exact error semantics, the explicit list of returned fields, and the coordinate/location conventions (1-based inclusive, strand, spliced length, original location descriptor). This is genuinely useful transparency for an agent deciding how to interpret results.

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?

The description is dense but well-structured: it opens with the core action, lists return contents compactly, then covers accepted identifiers and error behavior. Every sentence adds operational value, and nothing is wasted.

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?

For a single-record read operation with no output schema, the description covers all the essentials: what is returned field-by-field, what identifiers are accepted, how errors behave, and the effect of the optional parameter is already in the schema. No critical gap remains for an agent to invoke or interpret the tool correctly.

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?

Input schema coverage is 100%, and the schema already documents both parameters, including examples for id and the use case for includeSequence=false. The tool description reinforces the identifier alternatives but does not add meaning beyond the schema. Baseline 3 is appropriate because the schema carries the parameter documentation burden.

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 states a specific verb and resource ('Return one vector from the library') and enumerates exactly what is included, from accession and sequence to the full feature table. Its singular scope and explicit content list clearly set it apart from sibling search tools like vector_library_search without needing to name them.

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?

The description clearly indicates when to use the tool: to retrieve a single known vector by library id, name, or accession. It also gives behavioral guidance on error handling — unrecognised ids produce a closest-names error rather than an empty result. It does not explicitly list alternatives or exclusion cases, but the exact-identifier framing is sufficient.

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