Validate API Key / Current User

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully covered. The description adds useful context about what the validation returns (account name, premium/supporter, rate limit), which goes beyond the annotations. However, it doesn't disclose details like whether the key is read from an environment variable or how errors are reported.

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?

One sentence, front-loaded with the primary action ('Validate NEXUS_API_KEY'), and every clause adds value: what is validated, what account info is shown, and what rate-limit info is included. No wasted words.

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 zero-parameter, read-only validation tool, the description is nearly complete. It covers the purpose, the implicit input (NEXUS_API_KEY), and the output (account name, premium/supporter, rate limit). It doesn't mention error behavior or how the key is provided, but those are minor gaps given the tool's simplicity and the annotations covering safety.

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, so the schema is empty and there is nothing to document. The description explains what the tool does with the implicit NEXUS_API_KEY, which is the only relevant input. With 0 params, a baseline of 4 is appropriate.

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 ('Validate') and resource ('NEXUS_API_KEY'), and clearly distinguishes this from sibling tools like get_user or web_login by focusing on API key validation and account status. It also specifies what the tool shows: account name, premium/supporter status, and remaining rate limit.

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 this is the tool to use when you need to check if an API key is valid and see account/rate-limit info. It doesn't explicitly name alternatives or exclusions, but the context is clear enough given the sibling list (e.g., get_user is for user profiles, web_login for browser sessions).

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