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

The description discloses the auth mechanism (NPKI certificate), the side effect of logging in, and the return value (API_KEY for chaining), which goes beyond the minimal readOnlyHint/destructiveHint annotations. It does not contradict the annotations, and the additional context is meaningful for calling downstream tools.

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 concise sentences deliver the critical ordering, the authentication method, and the return value without unnecessary detail. The most important usage instruction 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?

For a single-optional-parameter login tool with no output schema, the description adequately explains the return value and how it should be used for chaining. It could additionally clarify session lifecycle or re-login behavior, but the essentials are present.

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?

The main description does not discuss account_link_id, but the schema already documents it thoroughly with 100% coverage, including optionality and multi-certificate guidance. Since the schema carries the parameter semantics, the description does not need to compensate further.

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 clearly states the action: 'Login to NHIS EDI via NPKI certificate' and identifies its role as the session entry point for this provider. It also distinguishes itself from sibling login tools by naming the provider and explaining that it returns an API key.

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?

'Call this FIRST before any other tool for this provider' is explicit sequencing guidance that tells the agent when this tool must be used. It does not explicitly name alternative login/status tools or state when not to call it, so it falls just 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.