API Tool Calls

Rounding Calculator

round_decimal

Read-onlyIdempotent

Round decimal strings exactly to decimal places, tens, hundreds or other powers of ten. Choose half away from zero or half even, including negative ties.

Example tool call

This call uses example arguments supplied in the tool’s input schema.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "text": "-2.5",
      "places": 0,
      "tieMode": "half-even"
    },
    "name": "round_decimal"
  }
}

Input Schema

Name	Required	Description
`text`	Yes	Up to 200 decimal digits with optional exponent -200 through 200.
`places`	No	Decimal places; negative values round to tens, hundreds etc.; default 0.
`tieMode`	No	Exact halfway rule; default half-away.

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

AddedOct 4, 2026

TDQS

A3.6/5.0

Behavior3/5

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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world behavior. The description adds useful tie-rule context, including negative ties, which goes beyond annotations, but it does not discuss edge cases like input limits or return behavior (covered elsewhere).

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?

Two tight sentences, front-loaded with the core operation and options. There is no filler, and every clause carries useful meaning.

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?

For a simple, deterministic rounding tool with rich annotations and an output schema, the description supplies the essential purpose and options. It lacks explicit alternative routing, but the annotations and schema cover safety and input details, leaving the definition largely complete.

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

Parameters3/5

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

Schema coverage is 100%, so text, places, and tieMode are already fully documented in the schema. The description restates the places and tie concepts without adding syntax or format details beyond what the schema provides; the baseline of 3 applies.

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 gives a specific verb and resource: rounding decimal strings to decimal places, tens, hundreds, or other powers of ten, with explicit tie modes. The scope is precise and mostly distinguishes it from other rounding tools like round_sig_figs, though it does not name that sibling explicitly.

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?

There is no explicit when-to-use or when-not-to-use guidance, and no alternative tools are named. The implied context is enough for an agent to infer basic use, but choosing between this and round_sig_figs is left to the schema and sibling list.

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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