Create Custom Conversion

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

Annotations already indicate readOnly=false and idempotent=false, so the creation side effect is implied. The description adds no behavioral context beyond that: it does not mention permissions, duplicate handling, validation errors, or what the response will look like. With no output schema, some behavioral or return-value disclosure would be valuable.

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 scannable, with a clear one-sentence purpose followed by a compact Args list. The enum list and rule example are useful and not excessive. The only minor redundancy is repeating enum values already present in the schema, but this does not hurt usability.

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 description covers all required inputs and gives enough detail to construct a valid request. However, it does not explain what the tool returns, how to interpret success/failure, or when to use it relative to other conversion-related tools. Given there is no output schema and the operation is a mutation, a bit more context would make it fully complete.

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 description coverage is only 33%, but the description compensates well for the required parameters. It clarifies the meaning of ad_account_id, name, pixel_id, lists all custom_event_type enum values, and gives a concrete JSON example for the rule parameter. It omits the optional response_format, but the schema already documents that parameter adequately.

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 and resource: 'Creates a custom conversion for tracking specific actions.' This clearly distinguishes the tool from siblings like meta_list_custom_conversions or meta_create_custom_audience by naming the exact resource type. It is not a tautology and adds meaningful 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?

No explicit guidance is given on when to use this tool versus alternatives. The phrase 'for tracking specific actions' implies a use case, but the description does not mention related tools such as meta_send_conversion_event, meta_list_custom_conversions, or pixel prerequisites. An agent is left to infer when this tool is the right choice.

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