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

Annotations already cover safety (readOnly=true, destructive=false, openWorld=true), so the description's value-add is the billing behavior: minimum 10 credits, and repeated requests may purchase data again. That is genuinely useful, but the cost claims conflict internally ('at least 10 credits' vs '1 credit per request' vs 'actual supplier units'), leaving the agent unsure of the real price.

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?

The first two sentences are well-structured and front-loaded, but they are followed by injected boilerplate that repeats the title, restates pricing inconsistently, and includes navigation artifacts ('API View Pricing', 'Examples are not guaranteed prices'). Roughly half the text does not earn its place.

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 one parameter and no output schema, the description does the heavy lifting by enumerating return fields (page_id, name, category, likes, verification, Instagram details) and flagging the credit cost. Only the ambiguous pricing statement keeps it from being fully complete for a simple lookup 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 100% and there is only one required parameter. The description adds a small clarification that the query is a company name rather than a generic keyword (the schema says 'Keyword to search for'), but nothing about matching semantics or partial-name behavior. Baseline 3 for full schema coverage.

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?

States a specific verb and resource (searches companies in the Meta Ad Library) and names the output (page IDs), which distinguishes it from sibling endpoints like social_facebook_ad_library_company_ads and search_ads that consume those IDs. The trailing pasted marketing text dilutes the signal but does not obscure the core purpose.

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?

The phrase 'returns their page IDs for use with other ad library endpoints' implies the sequencing: call this first to resolve a page ID, then use the ad endpoints. It does not explicitly name those alternatives or state exclusions, so it falls short of a 5.

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