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

Annotations already declare readOnly, openWorld, idempotent, non-destructive. Description adds non-obvious behaviors: 'Zero-cost schema discovery', 'No quota consumption, no API key required.' This gives operational context beyond annotations. No contradiction.

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 concise sentences, each informative: function, usage guidance, cost/auth. No fluff, front-loaded with the main purpose.

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 discovery tool with rich annotations and an output schema, the description fully covers purpose, when to use, and cost implications. No gaps apparent.

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?

Input schema has zero parameters, so baseline is 4. Description adds no parameter semantics but doesn't need to; the empty schema is self-documenting. Mention of 'all available tools' and 'access tiers' clarifies the scope of results, not parameters.

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 states 'List all available Ground Truth tools and their access tiers' – specific verb (List), resource (tools), and scope (access tiers). Distinguishes from sibling tools by being the discovery meta-tool.

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?

Explicitly advises to call this 'before making a tool call' to explore available verification tools. Adds that it's zero-cost, no quota, no API key, implying it's safe to call anytime. Does not explicitly list alternatives but the tool's unique role makes usage clear.

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