chart_get_visible_range

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

With no annotations provided, the description carries the full burden and does well: it declares 'SIDE EFFECTS: None (Read-only)' so the agent knows it is a safe read, and 'LIMITATIONS: Depends on active screen width and zoom level' warns that results vary with viewport state. It does not discuss failure behavior when no chart is loaded, but the safety and limitation disclosure is solid.

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 labeled sentences, front-loaded with the payload description, then routing guidance, then caveats. Nothing is wasted and the structure is 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?

There is no output schema, so the description must convey what comes back, and it does: a date range in unix seconds plus bar index boundaries. Combined with the read-only and viewport-dependency notes, an agent has everything needed to call and interpret this tool.

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 tool takes zero parameters, which is the baseline-4 case. The description correctly implies no input is needed and instead documents the output semantics (unix seconds, bar index boundaries).

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 precise verb and resource ('Get visible date range ... and bar index boundaries currently displayed on the viewport') and even specifies the units of the returned timestamps. An agent can distinguish it from the sibling chart_set_visible_range, which mutates the range rather than reading it.

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 WHEN TO USE clause gives concrete triggers ('before capturing screenshots or inspecting what portion of the historical timeline is in user view'). It stops short of naming the complementary setter tool or stating when not to call it, so it is clear context without explicit alternatives.

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