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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description only needs to add context — and it does, enumerating the returned payload (citation, design, strength grade, Loop parts with verdicts, citing answer pages, unfreeze.us page). It omits not-found/invalid-slug behavior, which is the remaining gap.

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?

A single sentence, front-loaded with the identifier and the tool's scope, with no filler. The trailing noun list of returned fields is long but every element is informative, though it reads densely and could have been split for scanability.

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 carries the burden of describing returns and does so thoroughly, including nested content like Loop parts and citing answer pages. The main omission is behavior when the identifier is missing or unmatched, which matters given that neither parameter is required.

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 are already documented with formats, examples, and maxLength. The description adds only that the slug comes from search_studies and that either key is acceptable — useful but marginal over the schema, so 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 resource fetch (one Atlas study) and the two exact lookup keys (slug or DOI), and distinguishes itself from search_studies by naming it as the source of the slug. The agent can immediately tell this apart from search_studies/get_answer without opening a 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 phrase "from search_studies" establishes the discovery-then-fetch workflow, and "or its DOI" signals the two alternative lookup paths. It stops short of stating when-not to use it or what happens if neither identifier is supplied (0 required params), but the intended context is clear.

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