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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered; the description goes further by adding 'Nothing is stored' (no persistence side effect) and 'Needs a credential' (an auth prerequisite not in the annotations). It does not discuss empty-result behavior or limits, but it meaningfully exceeds what the annotations convey.

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?

Three short sentences, front-loaded with the core behavior and ordering rule, followed by input-shape mapping and the credential prerequisite. Slight redundancy in re-listing the carried-over field names that the schema already documents, but the 'carry over' framing adds output information since there is no output schema.

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 characterizes the result (the intersection, ordered by the left list, in the saved-creator shape). It leaves minor gaps such as empty-result behavior and whether inputs may contain duplicates, but nothing that would cause a mis-call.

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 baseline is 3, but the description adds real meaning by explaining the provenance and mapping of the creator objects: search_creators output feeds these arrays, profileId is the creator id, and the remaining fields carry over. That helps an agent construct valid inputs beyond the per-field schema descriptions.

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 first sentence gives a precise verb and resource ('Keep the creators that appear in both lists') plus an ordering rule, which is a specific, unambiguous operation. It does not name a sibling to route against, but the operation itself is unique among the sibling set (save_list, get_list, search_creators), so an agent can place it correctly.

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?

'Nothing is stored' implicitly tells the agent this is a pure computation and that persistence requires a separate tool, and 'Needs a credential' states a prerequisite. However, it never explicitly says when to prefer this over search_creators/enrich_creators or how to persist the result, so usage is inferred rather than stated.

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