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

Annotations already establish mutation, idempotency, and non-destructiveness, and the description adds critical behavior beyond them: a named list is created if absent, and a stock belongs to one list at a time so naming another list moves it. This is exactly the kind of side-effect disclosure an agent needs for a mutation tool.

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 sentences, front-loaded with the action and default behavior, then the key invariant. Every clause carries useful information with no wasted words.

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?

For a two-parameter mutation tool with annotations and an output schema, the description covers the essential behavioral details: who the watchlist belongs to, default list selection, list creation, and move semantics. Nothing needed to call 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 coverage is 100%, so the baseline is 3. The description goes slightly beyond the schema by explaining the consequence of naming another list—that the stock moves rather than being duplicated—which clarifies the watchlist parameter's semantics.

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 names a specific verb and resource—adding a US stock to a watchlist—and immediately defines the scope as the signed-in person's StockMap. The move semantics and auto-creation of a named list make it unmistakably distinct from siblings like unwatch and my_watchlists.

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?

It gives clear situational context: use this to add a stock, optionally naming a list, with the default being the first list. It does not explicitly name alternatives or say when-not to use it, which keeps it short of a 5.

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