merge_custom_audiencesCombines 2 to 64 ready custom audiences from the same ad account into one new union audience, enabling broader targeting while preserving existing audience segments.
Merges 2 to 64 existing, ready audiences in the same ad account into a new union audience.
| Name | Required | Description | Default |
|---|---|---|---|
| name | Yes | Name for the merged audience | |
| idempotency_key | No | ||
| custom_audience_ids | Yes | 2 to 64 existing ready audience IDs |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations, the description carries the full burden. It discloses meaningful behavioral traits: the operation requires prerequisites ('existing, ready audiences'), is scoped to a single ad account, and creates a new union audience rather than modifying inputs. However, it does not mention whether the operation is asynchronous, what it returns, or how failures surface—gaps that matter given there is no output schema.
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 a single, front-loaded sentence with no filler. Every element—input count, input state, account scope, and output type—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 must convey return behavior, but it only says the result is a 'new union audience' without indicating whether an ID or operation status is returned. Given the sibling get_audience_operation_status and submit_bulk_mutation_job tools, the missing async/polling guidance is a significant gap for correct invocation.
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 67% with idempotency_key undocumented in both schema and description. The description adds useful semantics beyond the schema by clarifying the 'union' nature of the merge and reiterating the 'ready' precondition. Yet it does not explain the role of idempotency_key, leaving that parameter under-specified.
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 ('Merges'), a precise resource ('existing, ready audiences'), and the exact output ('a new union audience'). The constraints '2 to 64' and 'in the same ad account' further differentiate it from sibling tools like create_custom_audience or mutate_audience_membership.
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 context is implied through 'existing, ready audiences' and 'same ad account', but the description does not explicitly say when to use this tool over alternatives, e.g., create_custom_audience or submit_bulk_mutation_job. No when-not-to-use guidance is provided.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.