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fill_column_nulls

Replace missing values in a data column with a specified value to handle null or NaN entries during data preparation.

Instructions

Fill null/NaN values in a specific column with a specified value.

Returns: ColumnOperationResult with fill details

Examples: # Fill missing names with "Unknown" fill_column_nulls(ctx, "name", "Unknown")

# Fill missing ages with 0
fill_column_nulls(ctx, "age", 0)

# Fill missing status with default
fill_column_nulls(ctx, "status", "pending")

# Fill missing scores with -1
fill_column_nulls(ctx, "score", -1)

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
columnYesColumn name to fill null values in
valueYesValue to use for filling null/NaN values

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
successNoWhether operation completed successfully
operationYesType of operation performed
transformNoTransform description
part_indexNoPart index for split operations
nulls_filledNoNumber of null values filled
rows_removedNoNumber of rows removed (for remove_duplicates)
rows_affectedYesNumber of rows affected by operation
values_filledNoNumber of values filled (for fill_missing_values)
updated_sampleNoSample values after operation
original_sampleNoSample values before operation
columns_affectedYesNames of columns affected
Behavior3/5

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

With no annotations provided, the description carries full burden. It clearly describes the mutation behavior (filling nulls) and mentions the return type 'ColumnOperationResult with fill details', which adds useful context. However, it doesn't disclose potential side effects, permissions needed, or whether the operation is reversible.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Perfectly structured with a clear purpose statement upfront, followed by return information, then practical examples. Every sentence earns its place - the examples are particularly valuable for showing different use cases without being redundant.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool has an output schema (implied by 'Returns: ColumnOperationResult'), the description doesn't need to explain return values in detail. With 100% schema coverage and clear examples, it provides good context for a data transformation tool. The main gap is lack of explicit guidance on when to choose this over similar tools.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the schema already documents both parameters well. The description adds value through multiple concrete examples showing different data types for the 'value' parameter (string, number, default status), which helps illustrate semantic usage beyond the schema's technical definitions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the specific action ('Fill null/NaN values') on a specific resource ('in a specific column') with a specific mechanism ('with a specified value'). It distinguishes from sibling tools like 'fill_missing_values' by specifying it operates on a single column rather than potentially broader operations.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage when null/NaN values need to be replaced in a column, but doesn't explicitly state when to use this versus alternatives like 'fill_missing_values' or 'update_column'. The examples provide context but no explicit guidance on tool selection criteria.

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

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