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

Annotations already declare the operation safe and idempotent (readOnlyHint, idempotentHint, destructiveHint=false), so the safety burden is covered. The description adds value beyond them by describing the returned payload (atlas product, plane of section, section thickness, dataset id) in the absence of an output schema, though it says nothing about rate limits, result size, or paging behavior.

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?

Two sentences, front-loaded with the verb and resource, with the second sentence providing the routing signal. Dense but not padded; the parenthetical product list is slightly heavy but earns its place by naming the atlas products.

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 no output schema, the description usefully summarizes what comes back and identifies the dataset id as the key to downstream image/expression fetches. Six parameters exist but all are documented in the schema, so the description is complete enough for an agent to call 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?

Schema description coverage is 100%, and each parameter (num_rows, start_row, product_id, gene_acronym, include_failed, plane_of_section) is already explained in the schema, including enum-ish values and defaults. The description adds no parameter-level detail beyond the gene scope, 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 opens with a specific verb+resource: 'List the Allen Brain Atlas in-situ hybridization expression experiments (SectionDataSets) for a gene,' and enumerates the attributes returned. It never names the near siblings (allen_search_genes, allen_structures), so it clears the bar for clarity but not explicit sibling differentiation.

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?

It gives a concrete use case ("where in the brain is gene X expressed") and a second one (finding experiment ids behind a figure), which tells the agent when this tool is the right pick. It stops short of naming alternatives or stating when NOT to use it, so it is clear context rather than full routing guidance.

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