Draft Performance Max signal changes

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

Goes well beyond the annotations (readOnlyHint=false, destructiveHint=false, openWorldHint=true) by disclosing that signals are hints rather than targeting, the cardinality limits (one audience signal, up to 50 search themes), the skip-if-present behavior, and the deferred-apply/dry-run validation model.

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?

Front-loaded with the action, then layered with constraints and lifecycle in dense, non-redundant sentences. Every sentence earns its place; the API link is terse reference.

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?

An output schema exists so return values needn't be explained, and the description covers the mutation lifecycle, cardinality rules, and validation path. Nothing material to correct invocation is missing.

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%, so the baseline is 3, but the description adds interaction semantics the schema lacks: replacing the audience requires removing the current one in the same draft, and already-present themes are skipped. This meaningfully clarifies how audience_id and remove_signal_ids relate.

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 (Draft adding/removing) on a specific resource (search themes / audience signal on a Performance Max asset group), distinguishing it cleanly from the read-side sibling get_asset_group_signals. An agent can pick it out without opening the schema.

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?

Explains the draft-then-apply workflow ('Nothing changes until confirm_and_apply applies the plan_id; a dry run has Google validate it'), which routes the agent to the correct next tool. It stops short of an explicit when-not-to-use or a named read alternative, but the usage context is clear.

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