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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so safety is covered. The description adds two useful behavioral facts: output is deterministic and delivered as inline SVG, and the chart renders retrograde/combustion/dignity flags. It does not disclose the size bounds (480-2400) or that a location must be resolvable, so it is adequate but not rich.

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?

A single, front-loaded sentence with zero filler; the output form and the notable flags come first.

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?

An output schema exists, so return values need not be described. However, for a 9-parameter tool with an anyOf location requirement and 0% schema coverage, the description omits the input-format guidance an agent needs to call it correctly, leaving it under-specified.

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 0% across 9 parameters, so the description carries the full burden and adds essentially nothing: no date/time format, no explanation of place versus latitude/longitude/timezone alternatives, no note on size or timezoneOffset. Only 'chart' loosely implies what the inputs feed into.

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 ('Renders') and resource ('South Indian chart') plus the output form ('inline SVG') and the extras embedded ('retrograde, combustion, dignity flags'). This clearly distinguishes it from the analyze_* siblings, which compute interpretations rather than produce a visual artifact.

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?

No guidance on when to choose this over siblings, and no hint about the either/or input modes (place vs latitude/longitude/timezone). The agent must infer placement entirely from the schema's anyOf.

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