Read the data of a DataLens chart

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

Annotations already declare readOnly/idempotent/openWorld, so the safety profile is covered. The description goes further by disclosing real behavioral traits: pivot tables are unsupported, the chart executes with its saved settings (no ad-hoc reconfiguration), and an unreachable source returns an error rather than partial data.

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?

Front-loaded with the return shape, then the mode of execution, limitations, and how to find a chart id — each sentence carries information. The trailing entries_list sentence is slightly tangential but functionally useful for argument discovery.

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?

There is no output schema, so the description must convey the return shape, and it does ('tables of columns and rows') plus the chartType discriminator describing how the output is produced. It stops short of covering result size, pagination, or row-limit behavior, which would matter for a data-returning tool.

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 both chart_id and params documented in the schema itself, so the baseline of 3 applies. The description adds no syntax or format detail for params beyond the schema's 'one value or several' explanation, though it does indirectly confirm these are the chart's saved-parameter values.

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 resource and result: 'The data a saved chart shows, as tables of columns and rows,' which clearly distinguishes this read-data tool from the sibling chart-config getters (charts_wizard_get, charts_ql_get, charts_editor_get). It does not name those siblings explicitly, so an agent must infer that this returns rendered data rather than the chart definition.

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?

It supplies a routing hint for locating the required argument ('entries_list with the scope widget finds charts') and notes the chart runs with its saved settings, implying params are the only override. However, it never says when to use this over datalens_datasets_data_get or datalens_sqlqueries_run, so alternative selection is left to inference.

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