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

Annotations already indicate this is a mutating operation (readOnlyHint=false). The description adds useful behavioral context beyond annotations: it pre-checks for duplicates to avoid duplicate tickers. However, it does not disclose what happens on duplicate detection or if the watchlist does not exist, but the added value is meaningful.

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 two sentences, front-loaded with the primary action, and every word adds value. No redundancy or unnecessary detail.

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 simple tool with full schema coverage and no output schema, the description covers the core purpose, supported asset types, and duplicate behavior. It lacks details on return values or failure modes, but these are not critical for a straightforward add operation. Overall, it is complete enough for an agent to select and invoke the tool correctly.

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 all parameters are already described. The description does not add new meaning beyond the schema; it only reinforces asset type support, which is already in the asset_type enum. Baseline 3 is appropriate since the schema carries the parameter documentation burden.

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 adds an instrument to a Stock Tracker, with a specific verb and resource. It distinguishes from siblings like remove_from_watchlist and create_watchlist by focusing on the add action and supported asset types.

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 implies when to use this tool (adding stocks, ETFs, or crypto pairs to an existing tracker) but does not explicitly mention alternatives or exclusions. The context is clear but lacks direct guidance on when NOT to use it or prerequisites like creating a watchlist first.

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