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

Annotations only declare readOnlyHint and openWorldHint; the description adds real behavioral detail beyond that — short links are expanded (implying outbound fetching), order is preserved, and overlapping endpoint stops are deduplicated. It does not cover failure modes for invalid or unreachable links, which is the remaining gap.

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?

Three short sentences, all load-bearing: purpose and motivation first, then two behavioral guarantees. No filler or restatement of the tool name.

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?

No output schema exists, and the description does at least indicate the result is a single combined link. It stops short of specifying the exact return form (URL string vs. object) or error behavior when a link cannot be expanded, a minor gap for an otherwise simple two-parameter 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?

Schema coverage is 100%, with both parameters documented including the minItems 2 / maxItems 25 bounds. The description reinforces ordering ("all stops in order") and the overlap rule, but the latter merely restates the mergeOverlap schema text, so it adds little beyond the schema — baseline 3.

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 ("Merge several Google Maps directions links into one link") plus the motivating constraint (10-stop limit per route). It is clearly distinguishable from the sibling list_link_stops, and the output shape (one combined link) is stated up front.

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 trigger condition: use this to get past the 10-stop limit per route. It also notes that short links are accepted/expanded, which prevents an agent from pre-resolving them. No explicit when-not or named alternative, so not a 5.

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