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

Annotations already declare the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=false), so the bar is lower. The description adds a genuinely non-obvious behavioral trait: the chart is live, re-executing its SQL against the tabs on every view. It doesn't mention limits, failure behavior on invalid SQL, or chart-count constraints.

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?

Three sentences, each earning its place: the live-behavior hook is front-loaded, then the query-shape prerequisite, then the aggregation recommendation. No filler or restated field names.

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?

For an 8-parameter mutation tool with no output schema, the description covers the key unknowns an agent needs: that the chart is live, how columns map to axes/series, and the recommended query shape. It omits what is returned (e.g., a chart id) and any failure conditions, which are the remaining 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 coverage is 63% and the two chart-mapping fields (x, series) carry no schema descriptions, yet the description explains their derivation rule: first column = x axis, numeric columns = series, overridable by setting them explicitly. That is meaning the schema cannot express. It says nothing about type/stacked interplay or the workspace parameter, which the schema partly covers.

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 ('Adds a LIVE chart to a sheet') and immediately distinguishes the artifact from a static image by explaining the SQL re-runs on every view. Enough to separate it from siblings like napkin_sheets_view_chart or napkin_sheets_set_cells without opening any 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?

Gives a concrete prerequisite workflow ('Write the query with napkin_sheets_query first') and a preference ('Prefer aggregated queries (GROUP BY)'), which steers the agent before it commits. It stops short of explicit when-not-to-use guidance or a stated alternative to pinning a chart at all.

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