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

The annotations already establish read-only, idempotent, non-destructive, closed-world behavior. The description adds meaningful behavioral detail by listing exactly what is returned: total variations, referenced variables, unresolved variables, and rendered samples.

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 front-loaded and compact: it states the operation, return contents, and intended use in two efficient sentences. Every sentence contributes useful information.

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?

Given the tool's read-only preview nature, complete annotations, and lack of an output schema, the description is complete enough to call correctly. It explains the rendered output and usage context without unnecessary repetition.

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?

Schema description coverage is 100%, so the schema already documents template, vars, and samples, including the samples range and default. The description reinforces the template example and variable concept but does not add parameter semantics beyond the schema.

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 gives a specific verb and resource: expand a spintax template and render its Liquid merge tags. It also enumerates the outputs, making the tool's purpose unambiguous and distinct from the surrounding analysis and verification tools.

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 provides a clear usage context: "Use it to check a sequence before it sends." It does not explicitly name when not to use it or identify a sibling alternative, but no sibling appears to overlap directly.

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