chart

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explains a key behavior: automatically resolving the order book id from the instrument_id. It also discloses the return content (price points, previous close, returns). While it doesn't mention rate limits or error conditions, it is transparent about the core behavior for a read-only chart tool.

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 concise and front-loaded: the first sentence states the main purpose, the second lists allowed periods, and the third describes returns. Every sentence earns its place with no filler or redundancy. It is well-structured and easy to scan.

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 2-parameter tool with no output schema and no annotations, the description provides a solid amount of context: purpose, period options, and return fields. It does not explain edge cases like what 'ALL' means or timezone behavior, but it is largely complete for the likely use case. The absence of an output schema is partially compensated by the explicit list of return fields.

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 description coverage is 0%, so the description must compensate. It explicitly lists all valid period values (DAY_1, WEEK_1, MONTH_1, etc.), adding meaning beyond the schema's bare string type. It also clarifies that instrument_id identifies an instrument, and the 'resolves the order book id' note adds context for how this parameter is used. This is adequate for the two parameters.

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's purpose: 'Price time series for an instrument.' It specifies the resource (instrument), the data type (price time series), and adds a unique detail (resolves the order book id automatically) that distinguishes it from siblings like chart_by_identifier. This is a specific, non-tautological description.

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: to get price time series for an instrument, provide an instrument_id and optionally select a period. However, it does not explicitly state when to use this tool over alternatives like chart_by_identifier or indicators, nor does it mention any exclusions. The guidance is implied but not explicit.

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