create_combo_chart

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

No annotations are provided, so the description carries the full behavioral burden. It says nothing about permissions, whether the chart is persisted to the sheet, error behavior for invalid column/aggregation combinations, or whether the operation is reversible/removable (e.g., via delete_visual). For a mutation tool with zero annotation coverage this is a significant gap.

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?

Short and front-loaded: the action comes first, followed by a one-sentence clarifying definition and an example. The second sentence is borderline redundant with the parenthetical in sentence one, but it earns its place by disambiguating the 'sharing a category axis' semantics.

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 12-parameter, 9-required mutation tool with no annotations, the description does not cover prerequisites or constraints (e.g., that line and bar columns must be measures compatible with the aggregation, or that the sheet must belong to the given analysis). Adequate but with clear gaps.

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% with 12 well-documented parameters, so the schema already explains columns, aggregations, and format strings. The description adds nothing about parameters beyond a vague 'from simple parameters', leaving the baseline of 3 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 and resource ('Create a combo chart') and then defines the concept as 'bars + line on same chart', which cleanly distinguishes it from the sibling create_bar_chart and create_line_chart tools. An agent can tell what it produces without opening the schema.

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 example ('count bars with a percentage line overlay') implies a use case but there is no explicit when-to-use-this-vs-a-simple-bar-or-line-chart guidance, nor any prerequisites such as needing an existing sheet, analysis, and dataset. No exclusions or alternatives are named despite the many sibling chart creators.

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