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

Annotations already state readOnly, idempotent, and non-destructive, and the description builds on this by adding 'without consuming a credit,' which is a meaningful behavioral guarantee. It also warns against inventing billing dates and against adding the free allowance to credits_remaining, which are important edge-case behaviors. No contradiction 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?

Two focused sentences with no filler. The core action and no-credit side effect are front-loaded, and the second sentence adds only essential caveats about null dates and free allowance handling.

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 operation with an existing output schema, the description covers the core semantics, side-effect behavior, and important edge cases. Explicit sibling routing is not strictly necessary because the tool's purpose and scope are fully clear.

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 input schema has zero parameters and 100% schema description coverage, so there is nothing for the description to add about parameters. The baseline of 4 applies for zero-parameter tools; the description appropriately focuses on output semantics instead.

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 starts with a specific verb and resource: 'Read the authenticated user's Draconic plan and shared credit balance.' It is unambiguous about what the tool returns. It does not explicitly distinguish itself from sibling tools ask_draconic or get_coverage, but the resource scope is unmistakable.

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 clearly implies when to use the tool: when you need the authenticated user's plan or shared credit balance. It also gives practical guidance about null billing fields for free/test accounts. It does not name alternatives or exclusion conditions, but the narrow scope makes misuse unlikely.

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