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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds valuable behavioral context: output is a PNG image (not JSON), data is EOD only (doesn't reflect live intraday), and ambiguous symbols return candidate JSON instead of an image. These go beyond the schema and give the agent a realistic expectation of return types and edge cases.

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 dense paragraph that front-loads the primary purpose and then adds two important caveats (EOD-only and ambiguity handling). Every sentence contributes useful information; it's not overly long relative to the tool's complexity. The structure is logical and straightforward.

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?

The tool has no output schema, so the description must fill in return type details, which it does (PNG image vs JSON candidates). It covers the key edge case (ambiguous symbol) and the data recency limitation. However, it doesn't explicitly explain how the image is delivered (e.g., file path, base64), which is a minor but potentially relevant gap for an agent. Still, for a chart tool with well-documented params, this is largely complete.

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 coverage is 100%, so the schema already documents all four parameters with detailed descriptions. The tool description itself adds little beyond reinforcing the ambiguity handling already present in the symbol parameter. With full coverage, a baseline of 3 is appropriate; no additional parameter semantics are needed.

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 declares a specific action (render a candlestick + volume chart image) with a clear resource (CSE symbol data) and distinguishes it from describing raw OHLC rows, implicitly separating it from get_ohlc_data. It also notes the EOD-only limitation, which further clarifies what the tool is for.

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?

It explicitly tells the agent to 'hand this to the user directly instead of describing price action from raw OHLC rows,' which provides a clear use case. It also explains the ambiguity handling (returns candidates, ask user to pick). However, it does not name alternatives or give explicit when-not-to-use conditions beyond the raw-data comparison, so it falls just short of a 5.

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