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

Annotations are present (readOnlyHint=false, destructiveHint=false). The description adds meaningful context beyond annotations: the mandatory call ordering, the requirement of an existing account link, and the security note that secrets are never accepted as inputs. It does not contradict annotations and discloses key behavioral traits, though it omits session lifecycle details (e.g., expiration, failure handling).

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?

Three short sentences with zero redundancy. The most important instruction ('Call this FIRST') is front-loaded, followed by the purpose and a security constraint. Every sentence earns its place; nothing is missing or extraneous.

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 session-creation tool with one optional parameter and no output schema, the description covers the essential points: when to call, what it does, and a critical security constraint. The prerequisite (existing account link) is mentioned. No critical information for correct invocation is missing.

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 the schema already fully describes the single parameter (optional, auto-resolves, when to provide explicitly). The description only echoes the 'existing account link' concept without adding new meaning or format details. Baseline 3 is appropriate when the schema carries the parameter documentation.

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 a specific action ('Create a session') and resource ('KB Kookmin Bank fast-account inquiry session'), and distinguishes it from sibling login tools by naming the provider and the 'Call this FIRST' ordering. It is not a tautology and provides a concrete purpose.

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?

Explicitly instructs to call before any other tool for this provider, which is strong usage guidance. It does not explicitly state when not to use it or name alternative tools, but the ordering instruction is clear and the context (session creation) implies it is the entry point. Slightly less than a 5 due to missing exclusions.

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