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

Annotations already declare read-only, idempotent, non-destructive behavior, so the description earns credit for what they cannot say: results come from an algorithm rather than a database, 1 m precision, WGS84, and a coverage limit of 80 S to 84 N. The closing caution to verify against a map is genuine accuracy/risk context. Only the error behavior for bad input is missing.

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?

Front-loaded with the conversion and the input modes, and every subsequent sentence carries real constraints (precision, datum, latitude band, verification). 'FREE, no payment' is mild promotional padding that the annotations' title already conveys.

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 3-parameter stateless converter with no output schema, the description covers inputs, precision, coordinate system, and geographic bounds — enough to call correctly. It stops short of stating the return shape or the behavior on conflicting/invalid inputs.

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% and each parameter already carries its own description and range constraints. The description reinforces the lat/lon-or-mgrs mutual exclusivity, but adds no format or edge-case detail beyond what the schema states — baseline 3 is correct.

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 (convert) and concrete resource pair (lat/lon ↔ MGRS) in both directions, plus precision and datum. No sibling tool is remotely close, so the agent can identify it instantly.

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?

Explicitly says 'Send lat and lon, or mgrs', which tells the agent how to drive the two modes. It does not cover the failure cases (what happens if both or neither are supplied, or what happens for out-of-range coordinates), which one sentence would have fixed.

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