add_to_watchlist

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

With no annotations provided, the description fully carries the behavioral transparency burden. It explicitly states the operation is reversible, describes return values, and details error conditions (ValueError for empty item_id, TradingApiError for eBay-side errors). No contradictions with annotations.

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 well-structured with a clear opening sentence, followed by details in a docstring format. It is informative but slightly verbose; could be tighter while retaining all information.

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 simplicity (2 parameters, 1 required) and the presence of an output schema, the description covers parameters, returns, and errors adequately. However, it does not mention rate limits or authentication specifics beyond 'authenticated user'. Fairly complete.

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 input schema has 0% description coverage, but the description adds meaningful semantics: 'item_id: numeric eBay item ID (from search, get_item, etc.)' and 'host: configured host. Defaults to default_host.' This provides context beyond the raw 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?

The description clearly states the tool's action: 'Add an item to the authenticated user's watchlist.' It uses specific verb and resource, and distinguishes from the sibling 'remove_from_watchlist' by mentioning reversibility.

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 gives clear context for using the tool (adding to watchlist) and mentions the undo operation via 'remove_from_watchlist'. However, it lacks explicit guidance on when not to use this tool versus other siblings like 'get_watchlist' or 'search'.

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