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

The readOnlyHint annotation already establishes that this is a safe read operation, and the description is consistent with that. It adds useful domain context beyond the annotation by explaining that each envelope costs 1 credit, which helps the agent interpret the returned balance meaningfully.

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 concise and efficiently front-loaded: the first sentence states what the tool returns, and the second provides practical usage context. Every sentence earns its place with no filler or redundancy.

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 read-only tool, the description fully covers what the agent needs: what the tool does, what it returns, and when to invoke it. The output is implied by 'account name and remaining credits,' so no output schema is required for adequate 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?

The tool has zero parameters, so the schema is trivially complete and the description cannot add parameter-level detail. The baseline of 4 applies because the description accurately reflects the no-input nature of the operation.

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, 'Show,' tied to a clear resource: the GoodSign account name and remaining credits. This unambiguously distinguishes it from all siblings, none of which concern account or credit status.

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 gives explicit context for when to use the tool: before bulk sending or when the user asks about credit balance. It does not name alternatives, but no sibling tool offers account status, so exclusion guidance is unnecessary.

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