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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, covering the safety profile. The description adds meaningful context beyond those: that the data is 'end-of-day' (stale) and specifically that it is NOT real-time — which is a crucial behavioral caveat for agents expecting current prices. This is valuable addition beyond what annotations state.

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?

Two sentences, zero wasted words. The first sentence states what the tool does; the second sentence delivers the crucial caveat. Every word earns its place, and the key limitation is front-loaded in the second sentence.

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?

The tool is simple — a single required parameter, and an output schema exists. The description covers the key limitation (end-of-day, not real-time) that an agent would need to know. With the output schema present, return-format explanation is unnecessary. The only minor gap is not mentioning volume alongside price more explicitly in the caveat, but this is adequately complete for a simple read-only quote tool.

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% — the single 'symbol' parameter is fully documented with pattern, length constraints, and an example (AAPL). The description mentions 'one ticker,' reinforcing that a single symbol is expected. Since there's only one parameter and it's fully specified in the schema, the description doesn't need to add much; the baseline of 3 is slightly exceeded by the 'one ticker' clarification which reinforces single-input semantics.

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's function: 'Return the latest available end-of-day price and volume for one ticker.' The verb 'Return' plus the specific resource (end-of-day price and volume) plus the scope ('for one ticker') make it precise. It also distinguishes itself by explicitly noting it does not return a real-time quote, which helps differentiate from potential price-related 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 description explicitly says 'This tool does not return a real-time quote,' which sets expectations and tells the agent when NOT to use this tool (i.e., when real-time pricing is needed). However, it doesn't explicitly name alternative tools for real-time quotes or for historical data, though market_price_history is a nearby sibling. The single-ticker scope is implied as a usage constraint.

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