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

Beyond the readOnlyHint/openWorldHint annotations, it discloses the full result-state vocabulary (found, not_in_current_list, no_match_in_checked_list, unknown) and explains the ambiguous case as "seen before; reason not published or inferred." It also flags data limitations (no representative names) and the freshness caveat to verify on the ISA page, which materially changes how an agent should treat an answer.

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?

The question framing is front-loaded and the query modes, return values, and caveats each earn their place. It is dense rather than padded, though the return-value sentence is a long enumeration that could be tightened since an output schema already exists.

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 tabulate return fields, yet it still summarizes statuses and caveats, and it covers all lookup modes for a zero-required-parameter tool. The only minor gap is that the limit/default page size is unmentioned, which is low impact given 100% schema coverage.

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%, so the schema already documents the format of every filter including the override behavior of registration_number. The description restates the 2+ character minimum for names and gives the registration-number example but adds no semantics beyond the schema, 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?

The description opens with a precise question it answers ("Is this Specified Skilled Worker registered support organization in Japan's official ISA list?") plus a specific verb+resource (look up a registered support organization) and the lookup keys. It is clearly distinguishable from the sibling support_org_changes, which covers change history rather than identity lookup.

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?

It enumerates the query modes (registration number, name fragment, prefecture, language) and adds a caveat to confirm on the ISA page first, which gives implicit guidance. However, it never states when to prefer this tool over support_org_changes or catalog, nor any when-not conditions, so routing is left to inference.

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