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

Annotations already declare readOnly/idempotent/openWorld=false, so safety is covered. The description still adds valuable substance: what each finding contains, that confidence is attached, that these are 'signals only, never a buy or avoid verdict', and importantly 'does not browse the web' — clarifying the openWorldHint=false meaning. Good added context.

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?

Four sentences, front-loaded with the trigger condition, then returns, then exclusions, then parameter guidance. Dense but every sentence earns its place; the enumeration of brand types is slightly verbose but aids selection.

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?

Output schema exists, so return details need not be explained, and the description nonetheless summarizes the finding shape. Given annotations plus output schema, nothing an agent needs to invoke this correctly is missing.

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 coverage is 100%, so the baseline is 3. The description adds a genuine constraint not obvious from the schema alone: 'Pass brand names as the user or the listing gave them, up to 50 per call' — coaching formatting and echoing the 50 cap, which exceeds schema-only value.

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+resource ('Check brands') and enumerates what 'kind of brand' means (established name, store's own label, independent maker, generic white-label), distinguishing it from check_product/check_products which operate on products. An agent can select it confidently.

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?

Explicit when-to-use ('when the user asks whether a brand is reputable or what kind of brand it is... or wants brands compared while shopping') plus explicit when-not ('not for banking, health or email pages'). This is unusually thorough routing guidance.

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