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

The annotations already indicate this is not read-only and not idempotent. The description adds the crucial behavioral detail that the operation can remove an existing watchlist entry, not just add one. This is meaningful context beyond the structured annotations and helps the agent predict side effects.

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 entire description is one efficient sentence that states the action and the toggle behavior without fluff. Every part earns its place, and the key behavior is front-loaded.

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 single-parameter tool with an output schema and annotations already present, the description covers everything needed to invoke it correctly: what it does, the toggle side effect, and the only input. There are no significant missing details.

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 description coverage is 100%: the schema already specifies that 'symbol' is a stock code, ticker, or company name. The description adds no additional parameter-level meaning beyond that, so the baseline score applies.

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 states a specific verb ('Add') and resource ('company to the user's watchlist'), and immediately clarifies the toggle behavior: it removes the company if it is already present. This makes the tool's function unambiguous and distinct from the sibling tools, none of which target watchlist toggling.

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 makes the usage context clear: use this tool to add a company to the watchlist, and the same call will remove it if already present. It does not explicitly list alternatives or when-not-to-use conditions, but no sibling tool offers this watchlist-toggle capability, so the guidance is sufficient.

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