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

Annotations only supply readOnlyHint=false, openWorldHint=false, destructiveHint=false. The description adds substantive behavior beyond that: it saves a private draft after Google validate-only, captures a complete affected-resource snapshot, and does not send the change. These are meaningful operational disclosures. It does not say what the draft/snapshot looks like or how the prepared state is later consumed, leaving a small gap.

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?

Three tight sentences with no filler, front-loaded with the core action before the draft/snapshot detail and the confirmation hand-off. Every sentence 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?

For a no-output-schema prepare tool with a mutation-adjacent side effect, the description adequately explains effect, safety posture, and the required follow-up confirmation. It is only short on parameter semantics, which the (partial) schema partly covers.

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% (only customer_id is documented), and the description adds no parameter-level meaning at all. It never explains experiment_id or the affected_campaign_ids array (minItems 1, maxItems 2, unique), so with a nested required body object the description fails to compensate for the low coverage.

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 ('promote a Search experiment by copying trial settings to the control campaign') and immediately distinguishes itself from the sibling google_ads_experiment_promote_confirm. An agent can tell exactly what this does 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?

It explicitly routes the agent: this is the prepare step that 'does not send the change,' and 'the confirmation tool is google_ads_experiment_promote_confirm,' plus the requirement that 'execution requires the user's agreement in the conversation.' The when-to-use and when-to-use-the-alternative conditions are both spelled out.

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