fetch

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

With no annotations provided, the description fully bears the burden of behavioral disclosure. It clearly states that the tool does NOT make direct API calls to Meta, only returns records cached by 'search', and returns 'Record not found' if the record was not previously cached. This is transparent about its limitations and expected behavior.

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 well-structured and front-loaded, with the main purpose in the first sentence. It uses clear sections for limitations, alternative tools, arguments, and return value. Every sentence adds necessary value, and the length is appropriate for the complexity of the tool's behavior.

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?

Given that this is a simple tool with one parameter and no annotations, the description covers all essential context: what it does, its limitations, when to use alternatives, the parameter format, and the return value. It also works well with the existing output schema, making the tool self-explanatory.

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 only defines 'id' as a string with no description. The description compensates fully by explaining the exact format ('type:id', e.g., 'account:act_123456') and the requirement that it must have been returned by a previous 'search' call. This adds significant meaning 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 clearly states that the tool fetches a record previously returned by the 'search' tool in the same session, using a specific verb+resource+scope. It distinguishes itself from sibling lookup tools by explicitly noting it does NOT make direct API calls and only works on cached records.

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 explicit when-to-use and when-not-to-use guidance, including a list of alternative tools for direct lookups by ID (e.g., get_campaign_details, get_adset_details, get_ads, get_adsets). It also explains the critical prerequisite that the record must have been returned by a prior 'search' call.

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