Login Status

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

Annotations already declare readOnly, idempotent, and non-destructive behavior; the description adds that a credential is required, that the call is free at L0, and exactly what authentication data is returned: member/agent role, scopes, tier, expiry, method, and an opaque key prefix. This meaningfully goes beyond the annotations.

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 description is well-organized and front-loaded with purpose and usage before return details. Each sentence earns its place, though the L0 pricing note and credential clarification make it slightly longer than strictly necessary.

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 no output schema, the description carries the full burden of explaining return values, and it does so in detail. It covers when to call it, what it reports, and the credential requirement, making it complete for a zero-parameter read-only tool.

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 schema has zero properties and the description explicitly reinforces this with 'Takes no parameters.' It also clarifies that the credential is not a parameter but the subject being reported on, which removes potential confusion for an agent deciding how to invoke it.

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 states a specific verb ('Check') and resource ('the credential you are holding'), and explains that it distinguishes expired credentials from scope-based authorization failures. This clearly separates it from sibling tools like alter_verify and alter_whoami without needing to inspect their schemas.

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 gives explicit trigger conditions: 'when a call has failed on authorisation, or at the start of a session.' It frames the decision as expired credential versus unreachable scopes, but does not name specific alternative tools or explicit when-not conditions, so it stops 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.