read_cells

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

Beyond the readOnlyHint annotation, the description explicitly states 'Read-only: this function only reads workbook data and should not mutate files.' It also discloses the return type (dict or ChunkReadResult), error conditions (ValueError for missing/invalid mode), and internal dispatch mapping, which provides substantial behavioral context.

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?

The description is longer than average but well-structured with clear sections (Args, Returns, Raises, Notes) and bullet-style formatting. Every sentence adds functional value, and the opening line front-loads the core purpose. The length is proportionate to the tool's 14-parameter complexity.

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?

Given the parameter count (14), multiple modes, and presence of an output schema, the description fully covers usage, edge cases, and behavior. It includes format options, safety notes, error handling, and return type expectations. No critical contextual gaps are apparent.

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?

With 0% schema description coverage, the description carries the full burden of explaining parameters. It does so thoroughly, defining each of the 14 parameters, their purpose, and their mode-specific applicability (e.g., cell_ref for single reads, start_row/chunk_size for chunked reads). This fully compensates for the schema's lack of descriptions.

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 opens with a specific verb and resource: 'Read cell data from a worksheet.' It then clearly enumerates the three modes (single, range, chunked) and their distinct outputs, which distinguishes it from sibling tools like write_cells, clear_range, and get_sheet_summary.

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 description provides detailed mode-based guidance, specifying exactly which parameters are required for each behavior (e.g., 'single' requires cell_ref; 'range' requires start_cell and end_cell). It also advises chunked mode for large sheets. However, it does not explicitly name alternative sibling tools or state when not to use this tool, so it falls short of full alternative comparison.

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