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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false, and destructiveHint=false, so the safety profile is fully covered and the bar is lower. The description adds no behavioral detail beyond the safety data (e.g., deterministic pure formula, no external lookups), so it clears the lowered bar but adds little.

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 short sentences, no filler, with the core function stated first and the cross-reference second. Nothing needs trimming.

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?

An output schema exists, so return values need not be explained, and annotations cover the safety profile; the description plus structured fields are sufficient to call the tool correctly. The only minor omission is the underlying distance formula / result units, which would help a user interpret the output.

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%, with both parameters ('Apparent magnitude (m)', 'Absolute magnitude (M)') documented in the schema. The description restates the same two inputs without adding format, range, or unit nuance beyond what the schema already provides, so the baseline 3 applies.

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 ('Calculate star distance') and names the exact inputs ('from apparent and absolute magnitude'), which distinguishes it from near-siblings like calculate_light_year_distance and calculate_telescope_magnification.

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 pointer to list_bundles for related 'astronomie-nature' calculators gives some routing context, but there is no explicit when-to-use or when-not-to-use guidance, and no differentiation from the other star/distance calculators in the sibling list.

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