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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description adds behavior annotations do not: results are computed in code rather than read from pixels, only past windows are valid, and there is a hard 600-bar cap. It does not cover error behavior or latency.

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?

Purpose is front-loaded, but the body is one long run-on sentence with nested parentheticals, e.g. '(theirs — they may be used as levels the trader gave)', which is hard to parse and obscures the return shape. Information density is high but structure is poor.

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 carries the burden of explaining the return payload, and it does enumerate the returned sections (bars, indicators, marked levels/zones, envelope with draw gate, fact sheet). Coverage is good; minor ambiguity in the levels/zones parenthetical and no error/empty-window behavior keeps it from 5.

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 100%, so all five parameters are already documented (including defaults for indicators and the past-only constraint on 'to'). The description echoes those constraints ('indicators drawn', 'Past windows only') but adds little new syntax or semantics, so baseline 3 is correct.

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+resource+scope: what the chart would show for one market/timeframe/window, returned as a computed JSON object. It explicitly contrasts with the pixel-reading sibling ('Use it instead of reading pixels'), so an agent can distinguish chart_state from chart_image 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?

Gives a clear selection rule against the obvious alternative ('instead of reading pixels: every number is measured, not read') and adds operating constraints ('Past windows only; at most 600 bars'). It does not name the alternative tool explicitly or state when-not to use it, so it falls just short of 5.

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