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

Annotations already indicate readOnlyHint=false, destructiveHint=false, and idempotentHint=false, so the description doesn't need to restate those. It adds useful behavioral context: plan capacity limits, the result states the limit, and the tool does not execute trades or record holdings/transactions. It also clarifies the one-ticker-per-call constraint, which is beyond the schema's pattern. Minor gap: it doesn't describe the exact success/error response shape, but the output schema exists and the description covers the key behavioral traits.

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 three sentences, front-loads the core action and purpose, and every sentence earns its place. The capacity/plan note and the explicit exclusions are valuable and not redundant with the schema or annotations. 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?

Given the tool's simplicity (2 params, 1 required, output schema present, no nested objects), the description is nearly complete. It covers the action, scope, plan limits, and exclusions. The only minor gap is that it doesn't explicitly state what a successful response contains, but the output schema exists and the description's behavioral notes are sufficient for an agent to invoke 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?

Schema description coverage is 100%, so the schema already documents both parameters. The description adds value by reinforcing that exactly one ticker per call is allowed and that the exchange is optional and resolved automatically if omitted. It doesn't add much beyond the schema, but the baseline for high coverage is 3, and the description's explicit one-ticker constraint and exchange-resolution note push it to a 4.

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'), a specific resource ('one stock ticker to the authenticated user's StockLens watchlist'), and the purpose ('tracked and scored going forward'). It also clearly distinguishes itself from sibling tools by explicitly saying it does NOT execute trades, record a holding/transaction, or accept more than one ticker per call.

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 on when to use this tool (adding a ticker to a watchlist) and explicitly excludes related actions (trades, holdings, transactions). It also mentions plan capacity limits and directs users to stocklens.com for plan changes. However, it does not explicitly name sibling alternatives like remove_from_watchlist or discover_stocks, so the when-not-to-use guidance is implied rather than fully explicit.

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