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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower. The description nonetheless adds real behavior: null is returned when geometry is absent, schematic lines are flagged, and no figures are fabricated—important for trusting the payload. It stops short of describing the returned geometry's coordinate structure.

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?

Four short sentences, front-loaded with what is returned and followed by routing and behavioral caveats. Efficient overall; "Never invents figures" is slightly colloquial phrasing for "no fabricated values" but still earns its place.

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 one-parameter read tool with no output schema, the description covers return content, fallback behavior (null), data-quality flagging, and sibling routing. Only the shape of the GeoJSON payload itself is left implicit.

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 has zero description coverage and the single parameter is undocumented there, so the description must carry the load. It does clarify that the slug identifies a trail (not a region or permit), but it gives no format, casing, or lookup expectations, leaving some ambiguity unresolved.

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 ("Returns the stored line GeoJSON for a trail slug") and explicitly contrasts with the sibling get_trail, which serves summary facts. An agent can pick between the two without opening either schema.

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?

Gives an explicit selection rule ("Use when the client needs geometry") and names the alternative tool with its own condition ("use get_trail for summary facts"). This is the when-to-use/when-to-use-something-else pattern at full strength.

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