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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so safety is covered. The description adds two things beyond structured data: results carry a per-item 'scope' and that batch pricing should be compared against individual quotes - genuine behavioral context, though the latter is vague and never says how to obtain a quote (a check_price sibling exists but is unnamed).

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?

Two sentences, front-loaded with the capability and its limit, no filler. The long parenthetical type list is partly redundant with the schema enum and costs some density, but it does let an agent decision-check without opening the schema.

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 handling return shape and annotations covering read-only/idempotent behavior, the description needs only to explain batching, limits and per-item scope - all present. Missing is any guidance on partial failures or mixed validator batches, and the unexplained 'context-distill' option.

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% and each field is documented, so the baseline applies. The description's list of supported identifier families roughly mirrors the enum but omits one enum member, 'context-distill', leaving that option explainable only by the schema; the max-50 limit is likewise already in maxItems.

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 (validate identifiers) with a clear scope (up to 50, in one batch request) and enumerates the identifier families covered. The 'in one batch request' framing implicitly separates it from the single-check siblings (iban_check, lei_check, etc.), but it never names them, so an agent must infer the batch-vs-single distinction.

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?

The phrase 'Compare the current batch quote with individual quotes; savings depend on batch size' hints that this tool competes with per-item calls, but it frames the tradeoff purely in cost terms rather than telling the agent when to pick batch_validate over iban_check or lei_check. No explicit when/when-not, no note on whether a single-item batch is acceptable.

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