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

Annotations already establish readOnly and closed-world, so the description needn't restate safety. It adds genuine domain context — that a leg is a resupply-to-resupply segment, that the dataset is the 2021 walk, and that the response includes miles, length, days, dates, and a page reference.

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?

A single, dense sentence that front-loads the scoping fact (one of 26 legs). Nothing is wasted, though it could be slightly more scannable if the returned fields were separated from the definition.

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?

There is no output schema, so the description usefully enumerates the returned fields. For a one-parameter read-only lookup, that is nearly everything an agent needs; only retrieval specifics like missing-leg behavior are absent.

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 the schema already documents the 1–26 range with Campo/Canada endpoints. The description adds only that the legs correspond to the 2021 walk; it offers no further disambiguation of the `leg` parameter beyond what the schema 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?

The description identifies the resource precisely: a single PCT leg out of 26 walked in 2021, with the fields it carries. The verb is implicit (carried by the title 'Get a PCT leg'), and it doesn't explicitly contrast with siblings like find_by_trail_mile, but an agent can tell this is a leg-number lookup.

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?

Usage is only implied: you'd call this when you have a leg number between 1 and 26. There is no statement of when to prefer this over find_by_trail_mile or list_pct_points, and no exclusions or prerequisites are given.

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