add_to_watchlist

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

With no annotations provided, the description carries the full behavioral disclosure burden. It explicitly states idempotency ('safe to call even if already on watchlist') and the auth requirement ('Requires API key'), which are valuable traits beyond what the schema reveals. It does not mention rate limits or error behavior, but for a simple add operation, this is sufficient.

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 and every word adds value: the action, idempotency note, and API key requirement are all non-redundant. No fluff or repetition.

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?

This is a low-complexity tool with one well-documented parameter and no output schema. The description covers the core operation, a key behavioral trait (idempotency), and a prerequisite. There are no missing aspects that would prevent an agent from using it 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?

The input schema already fully describes the only parameter (symbol) with a good example. The description adds minimal additional meaning beyond restating that it is a ticker symbol, so it neither helps nor hurts. With 100% schema coverage, baseline 3 is appropriate.

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 action ('Add a ticker symbol') and clearly identifies the resource ('the watchlist'). It distinguishes itself from sibling tools like remove_from_watchlist and list_watchlist by conveying the write operation.

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 when to use the tool (to add a symbol) and notes a prerequisite (API key). It does not explicitly list alternatives or when not to use it, but the operation is well-scoped enough that no exclusions are necessary.

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