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

With no annotations provided, the description carries the full behavioral burden. It discloses that tolerance is in degrees, not metres, that endpoints are always kept, the nature of the return value, and that no network call or quota is involved. It does not cover edge cases or error behavior, but the provided details are useful and non-obvious.

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?

Every sentence in the description earns its place: the core purpose, the unit warning, the endpoint guarantee, the return value, and the local-computation note. It is compact, front-loaded, and free of filler.

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 two-parameter tool with full schema coverage and an output schema, the description provides all essential information: how to interpret tolerance, the guarantee about endpoints, and what the return contains. No critical gap remains for an agent to invoke it correctly.

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?

The schema already documents both parameters fully, so the baseline is 3. The description adds value by clarifying the tolerance unit conversion (degrees vs metres, with a concrete equivalence) and by stating that endpoints are always kept, which affects how the points parameter is interpreted.

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 uses a specific verb and resource ('Reduce the number of coordinates in a polyline while keeping its shape') and names the Douglas-Peucker algorithm. It clearly distinguishes geo_simplify from geometric calculation or measurement siblings like geo_length, geo_area, and geo_centroid.

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 gives clear context for use: simplifying a polyline by reducing coordinates while preserving shape. It also notes 'Local computation: no network call, no quota,' which is a practical usage consideration, though it does not explicitly mention alternatives or when not to use the tool.

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