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

Annotations already cover the safety profile (read-only, idempotent, non-destructive), and the description goes well beyond them: ordering (newest first), page size (25), the meta.count total, the meaning of every status value, skip_reason/error_code purpose, and the qualification fields. That is rich behavioral context an agent cannot get from the annotations.

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?

Purpose is front-loaded in the first clause, and every sentence carries information. The tier explanation is a dense run-on with heavy parentheticals, which slightly hurts scannability but not length-for-complexity.

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 and six parameters, the description still conveys return shape (the per-lead fields), pagination, ordering, and filtering. The page parameter is never explained, which is the one small gap for a paginated tool.

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 only 50%. The description compensates strongly for two of the six params by decoding the status enum (received/processed/contact_only/failed) and the tier enum, including the ambiguous "unscored" case. page and fields are not elaborated, though fields is covered in-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?

Starts with a specific verb+resource ("List Facebook Lead Ads leads") and immediately scopes it. It is clearly distinguishable from get_facebook_lead (single lead) and list_facebook_lead_forms siblings, and it states what the collection contains.

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?

"Filter by status, tier and date range" plus "Answers to the form are not included" give clear context for when this collection view fits and when it does not. It never names a sibling alternative, but the scope is unambiguous.

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