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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint=false), so the bar is lower, yet the description adds real context: drawings are anchored to bars with UTC times and prices, they are user-authored artifacts rather than signals, and there is a time-based reveal ('a film of the window lets each one appear as the clock reaches it'). That temporal behavior is valuable and not present in the structured fields.

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?

Two sentences, front-loaded with the resource definition before the behavioral nuance. Despite slightly literary phrasing ('a film of the window'), no sentence is wasted and the key concept is delivered immediately.

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 single-parameter, read-only tool with full annotation coverage, the description gives the agent enough to call it correctly and understand the temporal reveal of results. The absence of any return-shape detail is a minor gap given there is no output schema, but the anchoring explanation largely compensates.

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% with a single enum-constrained 'market' parameter, so the schema fully documents the input. The description's talk of bar/price anchoring enriches the mental model of the returned data but adds nothing about the market parameter itself, making the baseline of 3 appropriate.

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 identifies a specific resource ('the trader's own drawings on one market's chart') and enumerates the forms it takes (lines, boxes, paths, notes), so an agent knows this is the read side of the drawing feature. It lacks an explicit retrieval verb, but the resource is unambiguous and distinct from write-oriented siblings like draw/erase.

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?

Usage is only implied: the description establishes that these are the trader's existing drawings rather than signals, which nudges the agent toward a read/preview scenario. It never names alternatives such as draw, erase, chart_state or film, nor states when to prefer this tool over them, leaving routing to inference.

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