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

Annotations only declare readOnlyHint=true; the description adds genuinely non-obvious behavioral semantics — the sparse coverage set and the crucial distinction that 'not listed' means no venue coverage rather than flat/zero positioning. This is exactly the kind of context annotations cannot convey, though it does not describe response fields or freshness.

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 waste, with the core capability front-loaded and the coverage caveat immediately after. Every sentence earns its place.

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?

No output schema exists, but the description summarizes what is returned (funding, open interest) and the key pitfall, so an agent can call it correctly. Only minor omissions remain, such as field details or update frequency.

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% for the single ticker parameter, so the schema already documents it fully. The description adds no syntax, format, or constraint detail beyond what the schema provides; 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?

States a specific verb+resource: funding and open interest for a single ticker on the 24/7 perpetual venue. This clearly distinguishes it from siblings like list_equity_perp (enumerating names) and list_positioning, which an agent can differentiate without opening schemas.

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?

Gives strong when-to-use context by warning that most tickers are NOT listed (only ~51 of ~4,600) and reading a 'not listed' answer correctly. It stops short of naming an alternative tool to use instead, so it is clear context without explicit routing.

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