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

Annotations only cover readOnlyHint/openWorldHint; the description adds substantial behavioral context beyond them: the free/Pro gating per mode, the exact error payload on the free tier, and the date-boundary rules for what stays free. This is exactly the tier/authorization detail 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?

Front-loaded with the use case, then the return shape, then the tier rules — all useful. It is dense and runs long in a single trailing sentence, but no clause is 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?

With no output schema, the description still explains the return format (ASCII chart, two-hour blocks/days/months) and the tier-failure behavior. An agent has everything needed to choose and invoke it correctly.

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% and the `period` description already maps hourly/weekly/yearly to blocks, days, and months (including the Pro note). The description largely restates this, adding only the 'omit `date` for this week/year' default nuance, 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 (renders an ASCII energy chart) and explicitly distinguishes itself from narrative siblings by naming the exact intent that selects it ('visual overview rather than a narrative answer'). It even cites the sibling `intentions_ask_hour` as the source of the same hour-resolution scores.

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 concrete trigger phrases ('show me this week', 'chart for today', '看一下图') plus the negative condition (use narrative tools instead of prose answers). It further routes by tier, telling the agent which modes are free versus Pro and that a `subscription_required` error suggests alternatives.

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