watchlist_import_preview

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

The readOnlyHint annotation already signals no mutation, but the description adds real value by spelling out the two mode behaviors: merge appends missing entries, replace rebuilds the exact requested order. It does not cover failure behavior (e.g., what happens on bad symbols or layout mismatch) or the shape of the returned diff.

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?

Two tight sentences with the no-write guarantee front-loaded and the mode semantics following. Nothing wasted, though 'rebuilds exact requested order' is slightly terse and could be misread without the mode name adjacent.

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 carries the burden of explaining what a 'preview' returns; 'show membership/order changes' hints at a diff but doesn't confirm the return shape. It also omits that changes require a live browser target and that a layout-ID mismatch aborts before writing, both of which matter for correct invocation.

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?

Four of five parameters already carry schema descriptions; the description compensates for the undocumented 'mode' parameter by defining merge vs replace semantics precisely, which the bare enum does not convey. It adds nothing for watchlist_id, target_id, expected_layout_id, or entries, but those are already documented in 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?

Starts with a specific verb+resource combination ('Show membership/order changes for an import without writing'), which makes the preview/dry-run nature unambiguous. It implicitly separates itself from the write-side sibling watchlist_import via 'without writing,' though it never names that sibling.

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 phrase 'without writing' implies this is meant as a pre-flight check before an actual import, and the merge/replace clause explains which mode to pick for which outcome. However, it never explicitly states 'use watchlist_import to apply' or notes any prerequisites/exclusions, so the when-to-use guidance is only implied.

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