datanika-mcp

preview_connection

Preview first rows from a source table using connection ID, table name, optional schema, and row limit. Verify data before running transformations.

Instructions

Preview the first N rows of a table from a source connection.

Args: connection_id: The connection to query. table: Table name to preview. schema: Optional schema name. limit: Max rows to return (default 100).

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "connection_id": "<connection_id>",
      "table": "<table>"
    },
    "name": "preview_connection"
  }
}

Input Schema

Name	Required	Description	Default
`limit`	No
`table`	Yes
`schema`	No
`connection_id`	Yes

Output Schema

Name	Required	Description	Default
`result`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

AddedSep 17, 2026

TDQS

B3.4/5.0

Behavior3/5

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

With no annotations, the description carries the transparency burden. It communicates the core read-only preview behavior and the default row limit of 100, but it does not explicitly state that no data is modified, mention permission requirements, or describe error behavior.

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?

The description is compact and front-loaded with the core purpose, followed by a concise parameter list. Every line adds useful information with no filler or redundancy.

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

Completeness3/5

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

The output schema covers return shape, and parameter semantics are documented, so a basic call can be made. However, the absence of usage guidance, behavioral caveats, and annotation-backed safety information leaves the description incomplete for a tool with no annotations.

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 0%, so the description must compensate, and it does by explaining all four parameters: connection_id, table, schema, and limit. It adds meaning beyond the schema, especially the default value for limit and the optionality of schema, though lacks further format or constraint details.

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

Purpose4/5

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

The description clearly states the action ('Preview') and resource ('first N rows of a table from a source connection'). It does not explicitly distinguish itself from siblings like preview_transformation or query_connection, so it falls short of full sibling differentiation.

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

Usage Guidelines2/5

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

There is no guidance about when to use this tool versus alternatives such as preview_transformation, query_connection, or introspect_connection. No prerequisites, exclusions, or alternative selection criteria are provided.

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