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

Annotations declare readOnlyHint=true, and the description adds 'Pure math,' conveying a no-side-effect calculation behavior beyond the annotation. It also flags the distinction from Structure P&L, which helps set expectations about input requirements. It doesn't cover error cases or output format, but with the annotation covering safety, the added context is valuable.

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 two sentences, each earning its place: the first states the function and scope, the second highlights the operational difference from Structure P&L. No filler or repetition of schema details; the key facts are front-loaded.

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 moderate-complexity calculation tool with readOnlyHint, rich schema example, and sibling P&L tool, the description provides enough to select and invoke correctly. It explains the JSON body pattern, contrasts with P&L, and the 'Aggregate' verb implies the return value. It lacks explicit return-format info, but no output schema exists and the schema example partially covers inputs; the description is sufficiently complete.

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 input schema already provides a detailed example with spot and per-leg constraints. The description's mention of 'top-level `spot`' and 'per-leg `expiry`+`impliedVol`' restates the schema without adding new meaning. Baseline 3 is appropriate because the schema carries the semantic load.

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 opens with a specific verb and resource: 'Aggregate Black-Scholes position greeks ... for a multi-leg options structure,' clearly enumerating the greeks included (delta, gamma, theta, vega, rho, vanna, charm). It distinguishes itself from the sibling tool by stating 'Different body than Structure P&L,' differentiating it from post_structure_pnl.

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 explicit usage context: 'Pure math — pass legs as JSON.' It names the key alternative (Structure P&L) and clarifies the body difference: 'needs a top-level `spot` and per-leg `expiry`+`impliedVol`.' It does not explicitly mention when NOT to use it beyond the P&L contrast, so it falls slightly 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.