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

Annotations (readOnlyHint=false, destructiveHint=false) establish it as a non-destructive write; the description adds the critical behavioral fact that the chart is LIVE and its SQL re-runs on every view. It omits idempotency behavior (what happens when adding a duplicate chart) and error behavior on bad SQL, keeping it from a 5.

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, front-loaded with the defining trait (LIVE chart), then the workflow prerequisite, then the best practice. No filler and every sentence carries distinct information.

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 write tool with no output schema and 63% coverage, the description covers the crucial query-authoring semantics and the live-query model. It leaves return value and duplicate-handling unaddressed, but the annotations carry the safety profile.

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?

Despite 63% schema coverage, the description adds real meaning for the undocumented x/series mapping ('first column = x axis, numeric columns = series, or set x/series explicitly'). It does not clarify type, stacked, or workspace semantics, which the schema mostly handles.

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 the title reinforces it. It is clearly distinguishable from napkin_sheets_view_chart, though it never names a sibling explicitly, so it stops short of a 5.

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 workflow prerequisite ('Write the query with napkin_sheets_query first to confirm the shape') and a usage preference ('Prefer aggregated queries'). It lacks an explicit when-not-to-use or a named alternative for related tasks, so it is clear context without full routing guidance.

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