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

With no annotations, the description carries the full disclosure burden. It explicitly states 'This tool does NOT require authentication' and outlines the return structure. It does not mention caching, volatility, or error behavior, but for a read-only capability declaration this is reasonably transparent and not misleading.

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 separate WHEN TO USE and RETURNS sections, making it easy to scan. It is not overly long, though the opening sentence and the following 'Returns the full capability declaration' line are slightly redundant.

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 zero-parameter tool with no output schema, the description fully covers what an agent needs: when to use it, authentication status, and a detailed breakdown of the returned capability fields. Nothing essential is missing for correct invocation.

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 input schema has zero parameters and 100% schema coverage, so there are no parameters to document. The baseline for a zero-parameter tool is 4, and the description appropriately signals that no inputs or authentication are required.

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?

Clearly specifies the tool retrieves the seller agent's AdCP capabilities and supported protocols, and goes on to enumerate the major return categories (protocols, inventory, audience_data, pricing, discovery). This distinguishes it from sibling tools like get_partner_info, discover_inventory, or describe_endpoint, so an agent can select it without ambiguity.

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 an explicit 'WHEN TO USE' section listing three concrete use cases: discovering supported protocols, understanding audience signals, and getting MCP endpoint/discovery URLs. It lacks explicit when-not-to-use guidance or named alternatives, so it does not fully reach the top score.

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