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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive). The description adds genuinely useful context beyond them: "Free public data" signals no auth/credit cost, and it specifies the data sources and that one is a "last print" vs a "live mark," hinting at staleness differences.

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 tight sentences, front-loaded with what the tool returns, then when to use it, then input examples. No filler; each sentence carries information.

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 no output schema, the description still explains the returned content (spread in dollars and bps), the inputs, and the intended use case. For a single-parameter read tool with full annotation coverage, nothing essential 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?

Schema coverage for the single symbol parameter is 0%, so the description must compensate. It does so with concrete example values (AAPL, NVDA), making the expected input form clear, though it does not state casing or exchange-qualification rules.

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 computation (cross-venue basis for a symbol) and defines both legs of the comparison: equity last print vs live perp mark. This cleanly separates it from siblings like get_price and get_perp_prices, which each return only one side.

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?

"Use it to spot venue dislocation without pulling both quotes yourself" gives a clear use case and implicitly contrasts with the two single-venue sibling calls. It does not name those alternatives explicitly, so it falls just short of a 5.

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