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

Annotations already declare the tool as read-only, idempotent, and non-destructive. The description adds valuable behavioral details: the 15-minute delay, 5m candle interval, and included data fields, enriching the agent's understanding beyond the annotations without contradicting them.

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 a single, well-structured sentence that leads with the most important selling point (FREE sample) and efficiently conveys the data type, delay, fields, and symbols. No unnecessary words.

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 simple preview tool with one parameter and no output schema, the description covers the essential aspects: data type, delay, content, symbols, and purpose. It does not specify the number of candles or time range, but this is minor for a sample.

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?

The schema has zero description coverage, and the only parameter (symbol) is fully enumerated with a default. The description merely repeats the allowed symbols without adding any new meaning or constraints, failing to compensate for the schema's lack of explanation.

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 provides a free sample of 15-minute delayed 5m candles with specific fields (close, USD volume, buy pressure) for ETHUSD or BTCUSD. It distinguishes itself from paid live tools and sibling candle tools by emphasizing its trial nature.

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 implies usage as a free trial before purchasing live tools, giving clear context. However, it does not explicitly name alternatives like get_candles or state when not to use it, leaving some inference to the agent.

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