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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered; the description adds genuinely new behavioral context by disclosing the coverage boundary ('in the laws japanlaw.org holds') and the per-result payload (law, designation, citing words, id, url). The instruction to link each cited provision by its fromUrl is useful output-shaping guidance. It stops short of saying what an empty result means or how limit/total interact beyond the schema, keeping it at 4.

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 purpose and scope are front-loaded before the invocation instructions, and no sentence is pure filler. The middle clause is dense and slightly tangled ('an id for fetch and its url; link each one you name by its fromUrl'), mixing payload description with output formatting in one breath, which costs a point.

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 100% parameter coverage, the definition only needs to add scope and routing, both of which it does, including the important caveat that coverage is limited to laws japanlaw.org holds. Its remaining gap is minor: no statement about what to do when nothing cites the provision, but that is largely covered by the output schema.

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 law, address, lang and limit are all already documented in structured form, including the three address notations. The description's only addition is a worked example ({"law": "labor-standards-act", "address": "Article 36(1)"}), which mildly reinforces the required pair but repeats what the schema already says.

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 verb and resource — 'Find the provisions that refer to a given one' — and then bounds the scope explicitly (same law, other laws, and the Cabinet/Ministerial Orders that set the details), plus the corpus limit 'every provision in the laws japanlaw.org holds'. That reverse-citation framing is clearly distinct from get_provision (fetch one provision) and search (find provisions), so an agent can select it without opening the schema.

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 tells the agent how to invoke it ('Call it with law and address, as get_provision') and supplies a concrete call example, which anchors the two required parameters. It does not, however, state when NOT to use it — e.g. that forward citations (what a provision cites) or plain text reading belong to get_provision/search — so the alternative routing is implied rather than spelled out.

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