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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds genuinely new behavioral context: the chart is rendered inside the chat, liquidity magnets are overlaid for crypto coins, and numeric data is returned alongside the visual. It doesn't address rate limits or whether the chart is ephemeral.

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?

Three short sentences, front-loaded with what the tool produces and ending with the usage trigger. Only mild padding in 'Also returns the numbers,' which is vague but cheap.

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?

With no output schema, the description should carry the return-value burden, and 'also returns the numbers' is too vague to tell an agent what data comes back or whether it needs to render separately. For a 2-param read-only chart tool this is adequate but leaves a real gap.

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 50% – symbol is documented but interval is not described in the schema beyond its enum. The description compensates slightly by enumerating supported market types (crypto, stocks, forex, commodities), implying flexible symbol formats, but says nothing about interval values or defaults.

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 concrete verb and resource ('Shows an interactive OwlChart candle chart inside the chat'), names supported markets, and adds the distinguishing behavior (liquidity magnets for crypto). This clearly separates it from data-only siblings like get_price_history by signaling a rendered chart artifact.

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?

'Use it when the user wants to see a chart' gives an explicit triggering condition. It stops short of naming alternatives (e.g. get_price_history for raw numbers) or stating when not to use it, so it lands at clear-context without exclusions.

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