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

Annotations already declare readOnly, idempotent, and non-destructive, so the safety profile is covered. The description adds two things the annotations do not: the response bundles related records that reference the entity, and the call is free (relevant next to paid siblings such as atlas_buy_pack). It still says nothing about errors for a missing id or result size.

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 with the primary lookup mode front-loaded and the alternate key and return scope packed into parentheticals. No filler and nothing an agent must read past to act.

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 one-parameter read tool with no output schema and full annotation coverage, the description covers the lookup key, the return scope, and the cost. The remaining gap is minor: no indication of behavior on an unknown id or the shape of the returned records.

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?

With one parameter at 100% schema description coverage, the schema already explains that id accepts 'a record id from a kit or search, or an emotion name.' The description restates the same duality without adding format, source, or resolution guidance beyond it, 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?

Names a specific resource ('one atlas record') and two lookup keys (record id or emotion name), plus the payload shape ('with the records that use it'). It is distinguishable from atlas_search in that it fetches a single known entity rather than querying, though it never names the sibling explicitly.

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?

'by id (or an emotion by name)' implies the precondition that you already have an identifier, which is a usable usage cue. However, it never states when to prefer this over atlas_search or atlas_kit, and the 'Free' note hints at a cost-based decision without saying how it selects against the paid siblings like atlas_buy_pack.

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