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

Adds substantial behavior beyond the annotations: the call returns a PREVIEW rather than applying, the asset keeps its ID and performance history, the new text propagates to all linked placements, and the preview pins current text so concurrent Google Ads edits cause nothing to be sent. That concurrency-safety detail is exactly the kind of context annotations cannot express.

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?

Four short sentences, each doing distinct work: purpose, identity retention, propagation, and concurrency safety. The preview behavior is front-loaded, and the trailing API reference costs almost nothing.

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?

For a mutation tool with annotations, full schema coverage, and an output schema (so return values need not be explained), the description covers the key agent-facing concerns: preview vs apply, side effects on the asset and its placements, and stale-preview handling.

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 100%, so asset_id, customer_id, and callout_text are already documented in the input schema. The description adds only general context about changing 'text' rather than any parameter-specific semantics, which is the baseline for fully covered schemas.

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 and resource: 'Draft changing a callout asset's text in place — returns a PREVIEW.' The 'in place' phrasing and the retention of asset ID implicitly distinguish it from draft_callouts, but no sibling is named explicitly, so it falls just short of full sibling differentiation.

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?

Clearly establishes the draft-then-apply workflow ('before the apply') and the preview-only behavior, which tells an agent when this tool is the right entry point. It does not explicitly name confirm_and_apply as the follow-up or draft_callouts as the create-new alternative, so there are no explicit exclusions.

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