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rrdmcp

rrdmcp

by wtnb75
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Python
Local

render_graph

Render a PNG graph overlaying specified plugin fields for a host between start and end times, enabling direct visual analysis of Munin RRD time-series data.

Instructions

Render a PNG graph overlaying the given fields of a plugin.

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": {
      "group": "<group>",
      "host": "<host>",
      "plugin": "<plugin>",
      "fields": "<fields>",
      "start": "<start>",
      "end": "<end>"
    },
    "name": "render_graph"
  }
}

Input Schema

NameRequiredDescriptionDefault
endYes
hostYes
groupYes
startYes
widthNo
fieldsYes
heightNo
pluginYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv0.1.0

TDQS

C2.8/5.0
Behavior2/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It states the output is a PNG graph but does not mention side effects, required permissions, behavior with invalid fields, time-range handling, or whether the operation is read-only. The description lacks the added context needed to understand the tool's runtime 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 a single, front-loaded sentence with no wasted words. It states the action, output format, and data source efficiently. Every part earns its place.

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?

For an 8-parameter, 6-required tool with no annotations and no output schema, a single-sentence description is insufficient. It doesn't explain what 'start' and 'end' refer to, what values 'group' and 'host' expect, or how fields are specified. An agent would need to guess at most of the required inputs.

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 compensate. It identifies 'fields' and 'plugin' as the data to plot, but says nothing about 'group', 'host', 'start', 'end', 'width', or 'height'. The description adds minimal meaning beyond the schema's parameter names and leaves several parameters ambiguous.

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 uses a specific verb ('Render') and a concrete resource ('PNG graph'), and mentions the data source ('given fields of a plugin'). This makes the tool's role clear and differentiates it from sibling listing/fetch tools, though it doesn't explicitly name a sibling. It stops short of a 5 because it does not draw an explicit contrast with related tools like fetch_series.

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 fetch_series or list_fields. No prerequisites, constraints, or exclusions are stated. The only usage signal is the inherent purpose implied by the verb, which is not enough to qualify as explicit guidelines.

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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