what_if

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

The annotations already declare readOnlyHint=true, and the description adds significant behavioral context: 'pure arithmetic over current holdings — no LLM call, instant, free.' It clarifies the tool has no side effects, is fast, and free, which goes well beyond the annotations. No contradiction.

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 well-structured: a short intro, usage guidance, parameter explanations, and return description. It is front-loaded with the key purpose and contains no unnecessary words. Every sentence adds value.

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?

Given the tool has only 3 parameters, an output schema exists, and the description covers purpose, usage, parameters, and returns, it is fully complete. Additional details like 'instant, free' provide useful context. No gaps.

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?

With 100% schema description coverage, baseline is 3. The description adds value by reiterating the mutual exclusivity constraint 'Provide exactly one of pct or price' and clarifying the symbol parameter as 'yfinance ticker held or tracked by the user' beyond the schema's description. This earns a 4.

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 purpose: 'Simulate portfolio P&L for a hypothetical price move' and distinguishes it from siblings by emphasizing it is a pure arithmetic simulation with no LLM call, instant, and free. This specificity and differentiation from tools like buy/sell/track earns a top score.

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 when to use: 'when the user asks scenario questions like "if the Nasdaq drops 10%, how much do I lose"' and provides clear guidance on parameters: 'Provide exactly one of pct or price.' While it does not explicitly state when not to use, the context makes it clear for hypotheticals, so it earns a 4.

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