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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds value beyond that by disclosing the shape of the result set (canonical links, release state, product status, conditional from-price, stock availability) and by drawing a hard content boundary ('catalog facts only'), which is behavioral guidance the annotations cannot express.

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 tight sentences with no redundancy: purpose first, payload second, scope boundary last. Every sentence earns its place and the front-loaded structure lets an agent decide within the first clause.

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?

An output schema exists, so return values need no explanation, yet the description still summarizes them usefully. With only three simple params and full annotation coverage, the only residual gap is the absence of named alternatives for guidance queries, which is a minor omission.

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%: q, limit, and response_format all carry their own descriptions with bounds and enum values. The description contributes nothing param-specific (no mention of query syntax, matching behavior, or what markdown vs json actually change), which is exactly the baseline 3 case where 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?

States a specific verb and resource ('Full-text search over the public catalog') and enumerates the returned facts (release state, product status, from-price, stock availability), so the agent knows exactly what comes back. It implicitly separates itself from the guidance-oriented siblings ('Catalog facts only, never use guidance') but never names them, so the sibling differentiation is partial rather than explicit.

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?

'Catalog facts only, never use guidance' is a real when-not condition, telling the agent this tool is wrong for guidance-shaped queries. However, it never names which sibling to use instead (e.g. defiance_evidence_lookup or defiance_policy_lookup), so routing must be inferred from the sibling names. Usage is implied rather than spelled out.

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