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

With no annotations, the description carries the full behavioral burden. It usefully discloses that hourly venues are normalized to the 8-hour equivalent, which is real behavioral context, but says nothing about auth, rate limits, freshness, or what the payload looks like.

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?

One dense sentence that front-loads the primary mode and appends the alternate mode. No filler or restatement of the title.

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 read-only data lookup with one optional parameter and no output schema, the description covers scope, venues, dual modes, and the slug convention. Return shape is unaddressed, which is a minor gap given no output schema exists to carry it.

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 0% (the lone slug parameter has only a maxLength), so the description must compensate. It does: it explains that slug selects single-symbol history and gives concrete examples (btc, eth, sol), adding meaning the schema lacks.

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 resource (perpetual funding rates), names the exact venues covered, and describes both operating modes (current cross-venue rates vs. single-symbol history). An agent can distinguish this from crypto_market or policy_rates without opening any schema.

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 clearly conditions usage on the slug parameter: omit it for current multi-venue rates, supply it for one symbol's history. It gives no explicit exclusions or named alternative tools, so it stops short of full routing guidance.

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