Derrick credits balance

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

Annotations already declare readOnlyHint=true. The description adds value by revealing it reads from an in-memory cache (no network round-trip) and returns the last known balance, potentially stale. No contradictions with 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?

Three sentences, each earning its place: purpose, behavioral detail, usage context, and a language instruction. No redundancy and front-loaded efficiently.

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 parameterless tool with no output schema, the description is largely complete. It explains caching and language handling, though it could optionally specify the return format (e.g., a number). Still, it provides sufficient contextual guidance.

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 no parameters, so the description cannot add parameter meaning. With 100% schema coverage and zero params, a baseline of 4 is appropriate as the description covers the tool's input needs.

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 clearly states that the tool shows 'the last known Derrick credits balance', using a specific verb and resource. It distinguishes itself from sibling tools like derrick_account, which would cover broader account info.

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 explicitly says 'Call this when the user asks how many credits they have left', providing clear context for use. It does not mention when not to use it or alternatives, but the guidance is sufficient for the tool's simple purpose.

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