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

Annotations already declare readOnlyHint=false and idempotentHint=true, so mutation and idempotency are covered. The description adds workflow context ('Required before activation') and output format ('Updated media buy with creative info attached'). It does not contradict annotations, though it omits failure modes or permission details—acceptable given the annotation coverage.

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 with clear sections (tool_description, when_to_use, combination_hints, output_format). It is front-loaded with the core action and every sentence earns its place, providing workflow, creative types, and output without unnecessary fluff.

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 tool with a nested object and no output schema, the description provides a complete workflow, output expectations, and creative type examples. The only minor gap is not specifying whether creative_ref and creative_data are mutually exclusive or complementary, but overall the description is robust for an agent to select and invoke the tool.

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 all parameters are documented. The description adds example creative types ('banner, native, snippet, video, text') and output expectations, but doesn't clarify the relationship or usage of creative_ref vs creative_data. This is marginal value beyond the schema, so a baseline 3 is appropriate.

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 clearly states 'Submit or update creative assets for an existing media buy' with a specific verb and resource. It also differentiates from siblings by noting it is 'Required before activation,' which distinguishes it from create_media_buy and activate.

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?

The description explicitly provides when-to-use guidance: 'After create_media_buy returns approved status. Upload creative before activating.' It also gives a workflow sequence 'create_media_buy (approved) → submit_creatives → activate' and lists accepted creative types, making usage context very clear.

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