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

Annotations already cover read-only/idempotent/non-destructive, and the description adds genuinely new behavior: EOD-only data, no live intraday, and the dual return mode where an ambiguous symbol yields JSON candidates instead of an image. That is exactly the kind of non-obvious behavior an agent needs before calling.

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 tight sentences with zero filler, front-loading the core action and the hand-to-user instruction before the caveats. Every clause carries information the agent needs.

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 still tells the agent what comes back — a PNG image normally, or JSON candidates on ambiguity. Combined with the data-freshness caveat, nothing needed to call and interpret the result is missing.

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% and each of bars, theme, interval, and symbol is already documented in the schema. The description only reinforces what the schema says (most recent `bars` periods, daily/weekly/monthly intervals) without adding syntax or default details beyond it, so the baseline 3 applies.

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 and resource — render a candlestick + volume chart image (PNG) for a CSE symbol — and immediately distinguishes itself from the raw-data sibling get_ohlc_data by saying to hand the image to the user rather than describe price action from OHLC rows. An agent can route to it without opening the 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?

Explicitly says to use this instead of describing raw OHLC rows, and states the constraint that it is EOD-only and does not reflect today's live intraday movement — a clear when-not condition. It also documents the fallback path for ambiguous symbols (ask the user to pick from candidates and call again).

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