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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, and the description adds valuable behavioral detail: missing scores may be absent, the watchlist is returned up to plan capacity, and tier_limited indicates truncation. These details go beyond the structured annotations and help the agent set caller expectations.

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 concise and front-loaded, with the core purpose in the first sentence and supporting behavior, limitations, and alternatives following in a logical order. Every sentence adds meaningful information; there is no redundancy with the schema or annotations.

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?

With zero parameters, a meaningful output schema, and annotations covering safety, the description still supplies the missing context: return semantics, absence behavior, plan capacity limits, and the correct sibling alternative. Nothing an agent needs to select or invoke this tool 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?

The tool has zero parameters, so the schema carries no semantic burden. The description reinforces this by explicitly stating that it does not accept ticker or filter arguments, which prevents agents from assuming optional inputs exist. This is slightly above the no-params baseline because it proactively clarifies the absence of parameters.

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?

States a specific verb and resource: 'Retrieve StockLens analysis summaries for the authenticated user's watchlist.' It explicitly distinguishes itself from discover_stocks by saying it does not rank or screen outside the user's watchlist, making sibling differentiation clear.

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?

Gives explicit use context ('Use this to give users an overview of their portfolio's analytical health') and an explicit alternative ('call discover_stocks for a market-wide ranked or filtered list'). It also states what arguments it does NOT accept, leaving no ambiguity about when to choose this tool.

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