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

Annotations already declare the safe-read profile (readOnlyHint, idempotentHint, non-destructive, closed-world), so the bar is lower, and the description still adds real context: the quote is cached, the evidence is precomputed, and no paid model or portfolio is touched. These details set expectations about data freshness and personalization that the annotations cannot express. It does not cover latency, error behavior for an unknown ticker, or output format, which keeps it below a 5.

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?

Three short sentences, led by the usage trigger the agent needs first, then the payload, then the boundaries. No filler and nothing redundant 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?

For a single-parameter read tool with no output schema, the description does the necessary work by enumerating what comes back and what the tool will not do. The main remaining gap is failure behavior for an invalid or non-US ticker, which an agent might want before invoking.

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% and the ticker property already documents the format with an example (NVDA), so the schema carries the parameter detail. The description adds only the constraint that the ticker must be 'explicit' and US-listed, which is mild but real value. Baseline 3 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 pairs a concrete retrieval verb with an enumerated payload: cached public quote, recent price chart, precomputed evidence, risk framing, and next questions. It also scopes the resource to 'one explicit US-listed stock or ETF', which implicitly separates it from the multi-ticker and market-wide siblings.

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 opening clause gives a clear trigger condition ('when the user asks about one explicit US-listed stock or ETF'), and the closing sentence supplies negative guidance (no paid model call, no portfolio access, no personalized recommendation). It stops short of naming an alternative tool for comparison or market-wide questions, so the agent must infer that from sibling names.

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