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

Goes well beyond the annotations by describing the default return set (availability, centroid, bounding box), the include_polygon effect, the fallback rule that 'historical geometry is returned first and successors are never substituted automatically,' and an unsupported feature. Annotations already cover the safe-read profile; this adds genuinely non-obvious behavioral context.

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 tight sentences with the scoping constraint and default-return behavior front-loaded. Every sentence carries information, though the density is high enough that it reads as a spec dump rather than a prioritized summary.

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?

With an output schema present, return values need no explanation, and the description covers the prerequisite, geometry-substitution rule, and unsupported year selection. The main residual gap is that the cap/rate behavior ('deployment-configurable') is left to the schema rather than summarized.

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%, so both loc_id/loc_ids and include_polygon are already documented in the schema. The description restates include_polygon's effect ('adds GeoJSON coordinates') but adds no format or syntax detail beyond what the schema provides, making the baseline 3 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+resource ('Shape lookup') scoped to 'exact existing loc_ids only', which implicitly distinguishes it from point-resolver siblings. However, it never names a sibling such as get_geography, so the agent must infer the boundary from the phrase 'exact existing loc_ids' rather than being told explicitly.

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?

Clear context: prerequisite 'Obtain any descendant IDs before this call', restriction to existing IDs, and the explicit limitation 'Year selection is not yet supported.' It stops short of naming the alternative tool for obtaining IDs, so routing is only implied.

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