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

Annotations already mark this read-only and non-destructive, and the description still adds real behavioral facts: a 500-lead per-reply cap, offset-based paging with pagination info in the reply, and that each call draws on the key's hourly API quota. It also discloses the underlying GET /leads/lead endpoint, which matters for open-world rate-limited APIs.

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?

Four sentences, each carrying distinct load: payload contents, page-size limit and paging, filtering options, and cost. The most decision-relevant facts (what you get, how big, what it costs) come first with no filler.

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 return-value burden and does so by enumerating the returned field groups and the 500-item page size with paging pointer. Safety is covered by annotations, cost by the quota note, and filtering by the date-window sentence, leaving nothing essential for a correct call unstated.

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%, so all six parameters including the date_type enum and interval bounds are already documented, making 3 the baseline. The description only loosely reinforces that a time window applies to signup, edit, login, or activity dates and that offset pages; it adds no format or interaction detail beyond the schema.

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 names a specific verb and resource ('List the account's leads') and defines the resource precisely as website registrants, plus the fields returned. That scope is enough to separate it from idx_get_lead (single record) and from the per-lead listers such as idx_list_lead_searches 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?

It gives concrete usage context: filter with a time window on one of four date bases, page with offset when a reply exceeds 500 leads, and expect it to consume an hourly API access. It does not explicitly say when to prefer this over idx_get_lead or idx_list_lead_searches, so no exclusions or alternatives are stated.

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