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

Annotations already indicate destructiveHint=true and idempotentHint=true, so the description's added value is the ownership restriction and the implied requirement that the chart exists. It doesn't contradict annotations and adds useful context beyond them.

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?

Two sentences with no filler. The primary action and key constraint are front-loaded, and every clause earns its place.

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?

Covers ownership, what can be updated, and that the chart is already published. However, it omits the 'narration' parameter from the list of updatable fields, and it doesn't clarify that plotly_spec is required. Since the schema carries those details, this is a minor but real gap.

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%, so the schema fully documents all parameters. The description mentions Plotly spec, title, and insight, which maps to three of five params, but adds no new meaning beyond the schema. Baseline 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 states a specific verb ('update') and resource ('existing chart you own'), and lists what can be modified ('Plotly spec, title, or insight'). It clearly distinguishes from siblings like publish_chart (creation) and get_chart (read).

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 states the ownership constraint ('Only the API key that created the chart can update it') and the context ('previously published chart'). It gives clear when-to-use guidance, though it doesn't explicitly name alternatives or exclusions, which would push it to 5.

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