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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), so the description focuses on non-obvious behavior: the atlas holds mouse and human as separate records for the same-but-differently-cased acronym, the attached expression datasets differ, and case-insensitive retry reports which casing matched. It does not discuss result shape or paging limits beyond what the schema states, keeping it short of 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 core action, then the authoritative/caveat sentence; every clause carries information and there is no filler. The second sentence is long and clause-dense, which slightly reduces readability but not content efficiency.

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 six-param, zero-required lookup tool with no output schema, the description covers the critical decision context (authoritative resolver, mouse/human separation, pre-requisite ordering). Return-value details are absent but arguably acceptable given there is no output schema to anchor them; the remaining gap is minor.

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 all six parameters (acronym, name_contains, organism, entrez_id, num_rows, start_row) are already documented with examples and defaults in the schema itself. The description adds no additional syntax or format detail beyond restating the casing nuance the schema already carries, 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?

States a specific verb (look up) plus resource (genes in the Allen Brain Atlas gene catalog) and enumerates the three lookup keys (symbol/acronym, name substring, Entrez ID). It explicitly differentiates itself from the sibling allen_expression_datasets, so an agent can separate the two without opening either schema.

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 declares itself AUTHORITATIVE for resolving a gene to the Allen internal gene id and organism, and instructs 'Use this before allen_expression_datasets' — an explicit ordering and alternative. The mouse-vs-human record split is framed as the reason to call this first, which gives the agent a clear selection rule.

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