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

Rich disclosure well beyond the annotations: no persistence, a resampled track (13 GPX points -> 37), null elevations/timestamps, courseName taken from the GPX <name>, .gpx-only acceptance, and GarminError on an empty response. One tension: the annotations declare readOnlyHint=false while the description insists it saves nothing, though this is a conservative default rather than a dangerous reversal.

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 key fact (parses without saving) and dense with useful specifics; the bold emphasis and parenthetical example are efficient. It is slightly over-packed with endpoint/mechanism detail, but every sentence carries information an agent needs.

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 no output schema, the description takes on the burden of describing the return value and does so concretely (courseId: null, resampled track, null elevations/timestamps, courseName source), and it also covers error behavior. Nothing essential for calling it correctly is missing.

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 the schema already documents content, encoding, and filename, making 3 the baseline. The description adds only marginal parameter-relevant detail: the multipart field name `file` and the .gpx-only constraint on filename. It does not add format or syntax beyond the schema.

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 (parses a GPX file into a course) plus a critical scope qualifier (WITHOUT saving it, courseId: null), which cleanly separates it from siblings such as create_course_from_gpx and create_course. An agent can identify the operation and its non-persisting nature without opening any 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?

The 'WITHOUT saving it' / 'Parses only, saves NOTHING' framing implies the use case (parse/preview rather than persist), but the description never states when to choose this over create_course_from_gpx or create_course, nor any exclusions or prerequisites. Usage is implied rather than spelled out.

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