Authentication info

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

With no annotations available, the description carries the behavioral burden. It discloses a meaningful safety guarantee ('The raw token is never exposed') and clearly signals a read-only operation through 'Return information.' It doesn't explicitly state side-effect-free behavior or error handling for unauthenticated calls, but the listed output ('whether the token is valid') addresses the primary concern.

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 with no wasted words. The first sentence front-loads the purpose and output fields, and the second adds a useful security caveat. Every sentence earns its place.

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 simple, zero-parameter, read-only tool with no output schema, the description provides enough information about what is returned and the security posture. It doesn't specify exact field names/types or failure modes, but these are minor given the low complexity.

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 tool has zero parameters and schema coverage is effectively 100%, so parameter documentation is unnecessary. The baseline of 4 applies here; the description adds no param info because there is nothing to add.

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 ('Return information') tied to a clear resource ('current MCP authentication') and enumerates the exact fields returned. This clearly distinguishes it from siblings like auth_with_password, impersonate, or list_auth_methods, which perform different auth operations.

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?

The description implies a clear use case: when an agent needs to inspect the current MCP authentication context, token validity, or authenticated identity. It doesn't explicitly name alternatives or state when not to use it, but for a zero-parameter read-only status tool, the context is clear enough.

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