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

With readOnlyHint=true and openWorldHint=false already declared in annotations, the description adds meaningful behavioral context: it explicitly states 'Priced per campaign, so no price is returned' and routes the agent to submit_campaign_brief for quotes. It also enumerates the returned content categories. It could go further by noting any authentication or rate-limit concerns, but for a read-only detail tool this is strong supplementary disclosure.

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 three sentences, front-loads the core purpose, and every sentence earns its place by either listing return contents or clarifying pricing behavior. The first sentence is dense but not wasteful. It could be slightly tighter, but the structure is effective.

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 read-only single-resource tool with no output schema, the description fully explains what the returned detail includes (product identity, ad placements, creative formats, targeting options, caveats, capabilities) and explicitly covers the pricing caveat. Combined with annotations covering safety, an agent has everything needed to call and interpret this tool correctly.

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%, and the single slug parameter is fully documented in the schema ('Channel slug from list_channels, e.g. "geo-targeted-mobile"'). The description itself adds no additional parameter semantics beyond referencing the product concept. This is the expected baseline when the schema does the heavy lifting.

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 the specific resource ('one paid media product') and enumerates exactly what the full detail contains: what it is, where ads run, creative formats, targeting, caveats, and capabilities. It also distinguishes the tool from submit_campaign_brief by clarifying that pricing is not returned here. An agent can immediately tell this is a read-only detail fetch for a single channel.

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 gives clear context ('the limits and prerequisites a buyer should know before submitting a brief') and names the alternative for pricing ('submit_campaign_brief gets a quote'). It also points to list_channels as the source of the slug via the schema. However, it does not explicitly state when not to use this tool or any other exclusions, so it falls short of the top score.

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