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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, so the safety profile is covered. Beyond that, the description adds real behavioral context: exactly what each bucket means, how skip_reasons arise, and what qualifies as 'qualified' versus 'needs_review' or 'unscored'. It does not discuss auth scope or result volume, which keeps it out of the 5 range.

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?

It is a single dense sentence, but it is front-loaded with the purpose and nearly every clause (skip_reasons taxonomy, tier definitions, localization note) carries content the agent needs. The heavy nested parentheticals make it harder to scan than it needs to be, which is the only deduction.

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 rightly carries the burden of explaining return semantics and does so comprehensively, including tier definitions and the Spanish reply-language convention. Pagination or ordering behavior is unstated, which is a minor gap for an aggregation endpoint.

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 the baseline is 3, but the description goes beyond the schema by giving semantics to the `fields` enum values (received, processed, contact_only, skip_reasons, by_tier, by_day) and to the qualification tiers that those fields surface. The date defaults are already in the schema, so nothing is lost.

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 states a specific verb (summarize) and resource (this account's Facebook Lead Ads leads) plus the scope (a date range), and enumerates the metrics returned, which separates it from listing tools like list_facebook_leads or get_facebook_lead. It stops short of explicitly naming a sibling it must not be confused with, so it lands just below the top mark.

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?

Usage is implied by the purpose: use this when you need an aggregated overview of Lead Ads performance for a period. There is no explicit when-not guidance and no mention of the alternatives (list_facebook_leads for individual leads, get_facebook_campaign_insights for ad spend), so selection still requires inference from sibling names.

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