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

Without annotations, the description carries the full burden. It discloses the return structure ('Returns: {light_years, parsecs, au, km, original}') and the conversion action. For a calculation tool, no side effects or destructive actions are expected. The description is transparent about what the tool does and returns.

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, front-loaded with purpose and action. Every word is useful. The mention of list_bundles is a helpful pointer without being verbose.

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?

The description, combined with the high schema coverage and output schema, provides adequate completeness for a simple conversion tool. It covers purpose, parameters, return values, and related tools. Minor gap: no mention of the positive-only constraint on value, but that is in the schema.

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 coverage is 100% with descriptions for both parameters. The description restates the units but adds no additional semantics beyond the schema. The return fields are described, which provides context for output, but the description does not clarify constraints like exclusiveMinimum >0 on the value parameter.

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 'Convert astronomical distances between light-years, parsecs, AU, km.' This specifies the verb and the resource. It distinguishes from other conversion tools (e.g., convert_distance) by focusing on astronomical units, though it does not explicitly name its siblings or differentiate.

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 implies the tool is used for converting among the listed units. It provides a link to list_bundles for related calculators but does not explicitly state when to use this tool vs siblings like convert_distance, nor does it give when-not or alternative guidance.

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