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

Annotations already mark the tool as read-only/idempotent, but the description adds meaningful behavior: it returns a PNG image, it is the same card published to their own channel, and it requires a token because demo scope cannot serve charts delayed. This gives the agent operational and authentication context beyond the structured annotations.

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 front-loaded with the core identity and output type, followed by a clear usage directive and the kind list. It is slightly longer than necessary because the kind list repeats the schema, but each sentence carries functional information and none are filler.

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 simple one-parameter chart tool with no output schema, the description is complete: it states the output format, enumerates available chart kinds, explains when to use it versus data tools, and notes auth requirements. Nothing an agent needs to decide whether to invoke this tool 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?

The schema already fully describes the single kind parameter, including all allowed values and the default. The description repeats the same enum list without adding new parameter-level meaning, so it does not substantially exceed the schema coverage.

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 (US natural gas chart), the output format (PNG), and the concrete chart contents (LNG feedgas, storage, weather runs, etc.). It also separates this chart tool from the data-returning sibling tools by explicitly saying the numbers are available as data from other tools.

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 says to use the chart when a human is going to look at the answer, and directs agents to other tools for the underlying data. The token/demo-scope constraint adds a clear prerequisite and limitation, which is valuable for deciding whether this tool is usable in a given context.

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