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

Annotations only declare readOnlyHint and openWorldHint, so the description adds real value: it discloses the $0.002 USDC cost per successful call, the x402 payment rails (Base, Solana, Arc), and that failed calls are not charged — a material fact for an agent deciding whether to call. It also enumerates what is returned per facility. It does not discuss pagination or result caps beyond the schema's limit.

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?

A single front-loaded paragraph states the source, then coverage, then returned fields, then filters and pricing. The facility-type enumeration is long but functional; there is little wasted wording.

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, the description need not detail return structure, and it still summarizes fields for orientation. Pricing, coverage scope, and filters are all covered for a five-parameter, zero-required query tool. The only gap is explicit sibling routing guidance.

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%, with each of q, type, limit, state, and country documented in the schema itself, so the baseline is 3. The description reinforces the three filter axes and notes the DNA-lab-only website/phone fields, but adds no syntax or format guidance beyond what the schema already supplies.

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?

The description names a specific resource (AABB-accredited facilities from AABB public lists) and enumerates the covered facility categories — blood banks, transfusion services, immunohematology/molecular labs, cord blood, HPC/cell therapy, DNA testing. The verb 'list/filter' and the returned fields are clear. It stops short of explicitly distinguishing itself from the nearest sibling, health_clia_laboratory_finder, so it lands at 4 rather than 5.

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?

'Filter by state, country or name' implies how to narrow a query, but there is no statement of when this registry is the right choice versus CLIA lab finder or the FDA mammography facility tool. Usage is inferable from the domain wording rather than stated.

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