Verify credentials and upstream reachability

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

Annotations already supply readOnly, idempotent, and openWorld hints, so the bar is lower. The description adds valuable behavioral detail beyond those hints: it resolves credentials the same way real tools do, makes exactly one authenticated request, reports the credential source, distinguishes failure modes, and explicitly says it never returns the credential. This is strong additional transparency.

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?

Every sentence earns its place: behavior, reported outputs, trigger condition, and safety guarantee. The description is front-loaded with the core action and remains concise despite covering subtle failure-mode distinctions.

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?

Given zero parameters and no output schema, the description fully covers what the agent needs: what the tool does, what it returns, how to interpret results, when to use it, and that it never exposes credentials. Nothing essential 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?

There are zero parameters, and schema coverage is 100%, so description carries no parameter burden. The baseline for zero-parameter tools is 4, and the description does not need to explain inputs. It stays safe rather than claiming extra credit for describing non-existent parameters.

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 uses a specific verb-resource pairing: it resolves the credential, makes one authenticated request to creditkarma.com, and reports diagnostic results. It clearly distinguishes itself from the sibling transaction and query tools by being a health check that diagnoses which hop broke.

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 explicitly states when to call it: 'Call this when a real tool fails and you want to know which hop broke.' It gives clear context for use but does not explicitly name alternatives or state when not to use it, though the diagnostic purpose makes the boundary fairly obvious.

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