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

Annotations already declare readOnlyHint and idempotentHint, so the safety profile is clear. The description adds the 'requires matplotlib' dependency and demonstrates parameter customization via examples, providing useful behavioral context beyond the annotations. It does not detail return values or side effects, but this is a minor gap given the annotation coverage.

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 concise: one clear purpose sentence followed by two short, illustrative examples. Every sentence earns its place, and the structure front-loads the primary purpose while using examples to show parameter usage without redundancy.

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 description is sufficient given the rich schema and annotations, covering the tool's purpose, dependency, and invocation pattern. It does not explicitly state what the function returns (e.g., a plot object), but for a visualization tool this is often implicit and not critical for correct invocation.

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 input schema provides 100% coverage with descriptions for all seven parameters, including examples. The description's code examples reinforce usage but do not add new semantic meaning beyond what the schema already offers, so the baseline of 3 is appropriate.

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 clearly states 'Create a scatter plot from data points' with a specific verb and resource, and the examples reinforce the use case. It distinguishes itself from sibling plot types like line chart, histogram, and box plot by explicitly naming 'scatter plot'.

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?

The description implies usage through examples (passing x_data and y_data arrays) but does not explicitly state when to prefer this over alternatives like plot_line_chart or plot_histogram. No exclusions or alternative recommendations are given.

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