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

Goes beyond annotations by detailing that it bills one vision check, runs a product+safety check, rejects lifestyle/scene shots, persists to a durable URL, reads the brand back to confirm, and reports what actually holds rather than what was asked. This adds substantial operational context beyond readOnlyHint=false and idempotentHint=true.

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 lengthy but every sentence carries essential detail (validation, billing, confirmation, failure behavior, parameter context). It is front-loaded with the core purpose and then elaborates systematically. No fluff, though it could be tighter without losing critical information.

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?

Given the tool's complexity (mutation, validation, billing, brand switching) and lack of output schema, the description covers all necessary aspects: what happens on success/failure, how results are reported, parameter guidance, and side effects. An agent gets everything needed to call it correctly without surprise.

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?

The schema provides descriptions for all parameters (100% coverage), so baseline is 3. The description adds important meaning: imageUrl must be a product shot, not a lifestyle scene; brandId switches the active brand like use_brand; source_note is a short note. This clarifies usage beyond the schema, though the schema already gives adequate descriptions.

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 ('Lock') and resource (product photo), and clarifies that it saves as the brand's default product, affecting future plan_ad/render_ad/generate_image calls. It explicitly distinguishes itself by explaining its role in grounding later tools on true packaging, which is unique among siblings.

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?

Provides clear context on when to use it: pass a product shot URL from specific sources (research results, workspace urls, etc.), and explains rejection criteria for inappropriate images. However, it doesn't explicitly name alternative tools or state when not to use it, though it implicitly contrasts with the read-back and active-brand switching like use_brand.

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