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

Annotations already declare read-only, non-destructive, open-world behavior, and the description adds real value on top: no key or sign-in required, a staleness flag is returned, and the tape is the same one vaults validate orders against. It does not define what 'stale' means or any rate limits, which keeps it short of a 5.

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 dense sentences with the key differentiator ('FREE, no key, no sign-in') front-loaded, immediately followed by capability and then the routing hint. No filler.

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 one-parameter read tool with no output schema, the description supplies everything needed: what is returned (price, close time, stale indicator), the market set, and the alternative for candle windows. Nothing material 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 is 100% and the single parameter is an enum with a description, so the schema already carries the semantics. The description restates the allowed tickers (NQ, ES, YM, BTC, ETH, SOL) but adds no format or edge-case detail beyond the enum itself — baseline 3.

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 and resource — the tape's latest price for one market — and specifies the returned pieces (1-minute close time, staleness). It explicitly distinguishes itself from the sibling tape tool, so an agent can tell them apart without opening either 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?

Names the triggering condition ('whenever an agent needs a current price') and the alternative with its constraint ('for a window of candles use tape (needs a key)'). Both when-to-use and when-to-use-something-else are explicit.

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