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

Annotations already declare readOnlyHint, idempotentHint and non-destructive, so the safety profile is covered. The description adds the conversion constant and states that it returns a converted distance, which is modest extra value, but discloses nothing about precision/rounding or supported ranges beyond the constant.

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?

Five short, front-loaded fragments with no padding; the purpose and conversion factor come first. It loses a point only because the 'Inputs: value, from, to' fragment is both wasteful and wrong, and a cross-reference to a bundle is buried at the end.

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?

Because an output schema exists, the description need not explain return values, and its single sentence there is harmless. But for a tool with an extremely close sibling it omits any disambiguation, and it contradicts the enum on supported units, leaving genuine gaps for correct invocation.

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%, so 3 would be the baseline, but the description actively misstates the parameters: it lists 'value, from, to' while the schema defines only 'value' and 'unit'. It also advertises miles conversion, which is absent from the enum (ly, parsec, au, km). This is misleading rather than merely redundant.

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?

States a specific verb and resource ('Convert between light-years and km/miles') plus the domain ('astronomy'), so the agent knows what it computes. However it never distinguishes itself from the sibling calculate_light_year_distance, which sounds like it does the same thing, so sibling differentiation is missing.

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?

'Use for astronomy' is a domain hint, not usage guidance. There is no indication of when to pick this over calculate_light_year_distance, calculate_star_magnitude_distance, or the generic convert_distance, and no exclusions are stated. The only routing hint points to list_bundles, which is a browsing tool, not an alternative calculator.

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