ping

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

Annotations already declare readOnlyHint and idempotentHint, so the safety profile is covered. The description adds value by stating that the call fetches the current user id and does not touch budget data, which helps an agent understand side-effect scope.

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 sentences with no filler, and the core action is front-loaded. Every clause earns its place by adding purpose or exclusion context.

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 no-argument read-only auth-check tool with an output schema and safety annotations, this description is fully sufficient. Nothing an agent needs to invoke it correctly 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?

The tool takes zero parameters, so the schema's empty properties object fully documents the input contract. The description appropriately focuses on output behavior rather than inventing parameters. Baseline 4 applies per the zero-parameter rule.

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 'Verify' and resource 'YNAB API auth' and defines the operational result ('fetching the current user's id'). It clearly distinguishes itself from budget-touching siblings by saying it leaves budget data alone.

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 identifies the use case: confirming YNAB_API_KEY is set and valid. It also gives an exclusion ('without touching budget data'), which guides an agent away from heavier tools. However, it doesn't name a specific alternative tool, so it gets slightly less than a perfect 5.

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