meta_ads_library

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

The annotation readOnlyHint=true already covers the safe read-only nature. The description adds that it returns active ad creatives, spend ranges, and targeting info, which is useful output context. It does not disclose any rate limits, pagination behavior, or the ambiguous 'config' parameter, but with annotations covering safety, this is a minor gap.

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 description is compact and well-organized: a clear purpose line, a brief output summary, and a concise Args block. It avoids redundant fluff while providing examples and defaults. Front-loaded with the most important information, every sentence earns 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?

The tool has no output schema, so the description's summary of return data is helpful. It covers the main parameters and gives a realistic use case. The main gap is the unexplained 'config' parameter and the absence of any mention of pagination or special constraints, but given the relative simplicity and readOnly annotation, the description is sufficiently complete for an agent to use it correctly.

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?

The input schema has no descriptions for its properties, so the description's Args section is essential. It explains query with examples, country as a two-letter code with a default, and limit as max results. However, it omits the 'config' parameter entirely, leaving its purpose undefined. With 3 of 4 parameters clarified, the description compensates well but not completely.

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 starts with a specific verb+resource: 'Search the Meta Ads Library for competitor ads on Facebook and Instagram.' It clearly distinguishes itself from siblings like google_ads_transparency and competitor_ads by naming the exact platform and use case. The additional output details (active ad creatives, spend ranges, targeting info) reinforce the scope.

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 description provides clear context: this is for searching Meta's ad library for competitor research. However, it does not explicitly mention when to avoid this tool or name alternative tools for other ad platforms. The context is sufficient for most cases, so a score of 4 is appropriate.

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