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

Annotations already declare readOnly/idempotent/openWorld, so the safety profile is covered. The description adds real value beyond that by disclosing the exact checksum algorithm used and that a signed XDR-1 receipt is produced, which hints at output provenance; it stops short of explaining failure behavior or what the signature guarantees.

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 short sentences, each carrying distinct information: what is validated, the standard applied, the use case, and the return artifact. No filler and the identity of the tool is front-loaded.

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?

With an output schema present and annotations covering safety semantics, the description supplies the domain context an agent needs to select it. The only omission is what an invalid code yields, which the output schema presumably covers.

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?

With one parameter at 100% schema coverage, the schema already documents the field name, length, and an example. The description reinforces the 18-character constraint and the checksum standard but adds no new parameter-level syntax or edge-case handling, so baseline 3 applies.

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 ('Validate') and a precisely scoped resource ('18-character Chinese business registration and tax code'), plus the governing standard (GB 32100-2015 ISO 7064 Mod-31-3). It is unmistakable against format-check siblings such as abn_check, cnpj_check, or gstin_check.

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?

Gives a concrete usage context: required for B2B supply chain trade with Chinese manufacturers. It does not name an alternative or exclusion (e.g., how it differs from china_supplier_check), so the routing guidance stops short of a 5.

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