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json_set

Update JSON data by setting a specified value at a dotted path, returning the modified document. Use to modify nested fields without rewriting the entire structure.

Instructions

Set a dotted path in JSON text or an object and return the document.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
dataYes
pathYes
valueYes

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

  1. First observed

TDQS

B3.3/5.0
Behavior3/5

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

The description discloses the main behavior (set a path, return the document), which is useful with no annotations present. However, it does not clarify whether the input is mutated in place, what happens if the path does not exist, how invalid JSON is handled, or how the returned document is formatted.

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 a single sentence with no filler. It front-loads the action and resource, and every word contributes to the tool's meaning.

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

Completeness2/5

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

The tool has three required parameters, no annotations, and no parameter descriptions, but the description only covers data and path semantics at a high level. Missing details about value encoding, error behavior, and output format leave the agent under-informed for a reliable call.

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

Parameters2/5

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

Schema description coverage is 0%, so the description must clarify parameters. It does explain that 'path' is a dotted path and 'data' is JSON text or an object, but 'value' is left ambiguous: it is unclear whether value should be a raw JSON string, a quoted string, or a serialized JSON literal. This is a critical ambiguity for correct invocation.

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 states a specific verb ('Set'), a precise resource ('a dotted path in JSON text or an object'), and the result ('return the document'). This makes the tool's core operation unmistakable and distinguishes it from siblings like json_get, which presumably reads, and json_merge, which combines JSON.

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?

No guidance is provided about when to use this tool versus json_get, json_merge, or any alternative. The agent must infer usage from the name and short description, and there are no exclusions or conditions given.

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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