High-level statistics for every column of a registered table: count, null_count, mean, std, min, max (DataFusion describe).
This tool declares no required parameters. Add optional parameters from the input schema as needed.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {},
"name": "column_statistics"
}
}| Name | Required | Description | Default |
|---|---|---|---|
| table | No | Table name (default: the first registered table) |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations exist, so the description carries the full burden. It usefully discloses that this is a descriptive/aggregate read operation and names the engine (DataFusion describe), but it omits whether this triggers a full table scan, cost/latency implications, or how nulls are handled in aggregates.
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?
One front-loaded sentence with the resource first and the returned metrics listed inline; nothing is redundant. It is appropriately terse, though a short clause on scope or cost would have earned its place.
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 a one-parameter, no-output-schema read tool this covers the essentials by enumerating the returned fields. It still leaves open what happens with zero registered tables, unregistered names, or whether the operation is expensive on large tables.
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 coverage is 100% and the single parameter's default is fully documented in the schema. The description adds no parameter-level detail beyond what the schema already provides, which is the baseline-3 case.
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 (computes high-level statistics) and resource (every column of a registered table) and enumerates the exact metrics returned. It does not explicitly distinguish itself from siblings like get_schema (which describes columns) or query_sql (which could compute stats manually), so it falls 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?
No guidance on when to use this versus get_schema or query_sql, and no mention of prerequisites such as having a registered table. Usage is only implied by 'registered table'.
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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