alltrails_list_completed_trails

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

The annotation readOnlyHint=true signals this is a read-only operation, so the description doesn't need to restate that. The description adds a subtle nuance: it says 'Defaults to the signed-in user; pass a userId to target a specific public profile,' which implies authentication might be needed for the default, but it doesn't clarify permission requirements (e.g., might fail for private profiles). This is minor additional context beyond the annotation, but it doesn't disclose potential errors or limits (e.g., pagination, rate limits), so a 3 is appropriate.

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?

The description is a single, well-structured sentence that front-loads the core purpose and then adds the optional parameter context. It is concise with no fluff, though it could be slightly more compact by combining clauses. Overall, it 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?

Given the tool's low complexity (single optional parameter), a high-coverage schema, and a read-only hint, the description is nearly complete. It explains the default behavior and how to target other users, which is essential for correct invocation. It doesn't cover potential edge cases like empty results or auth failures, but those are not strictly needed for a simple list tool.

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 the userId parameter fully (100% coverage), including its type and default behavior. The description echoes this but doesn't add much new semantic value—it just restates the default. Since schema coverage is high, the baseline is 3, and the description meets it without going beyond.

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 clearly states the tool's purpose: listing trails marked as completed by an AllTrails user. It specifies the main resource ('trails'), the action ('List'), and the modifier ('completed'). It also distinguishes the default behavior (signed-in user) from an optional override (specific user ID), which helps differentiate it from sibling tools that list other user content (e.g., alltrails_list_user_lists) or fetch single trails (alltrails_get_trail).

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 provides clear context on when to use the tool: to list completed trails for a user. It notes the default behavior (signed-in user) and when to pass a userId (to target a specific public profile). However, it does not explicitly state when NOT to use it or mention alternatives, such as using alltrails_list_user_lists for user-created lists, but the sibling list and tool names make the distinction inferable.

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