rendezvous-mcp

get-isochrone

Read-only

Compute a GeoJSON polygon showing area reachable from a point within a travel time by drive, cycle, or walk.

Instructions

Get a reachability polygon showing everywhere reachable from a point within a given travel time. Returns a GeoJSON polygon. Useful for understanding how far someone can travel.

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": {
      "lat": "<lat>",
      "lon": "<lon>",
      "transport_mode": "<transport_mode>",
      "time_minutes": "<time_minutes>"
    },
    "name": "get-isochrone"
  }
}

Input Schema

Name	Required	Description
`lat`	Yes	Latitude of starting point
`lon`	Yes	Longitude of starting point
`transport_mode`	Yes	Travel mode
`time_minutes`	Yes	Maximum travel time in minutes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.1.4May 3, 2026

TDQS

A3.8/5.0

Behavior3/5

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

The description mentions the tool returns a 'GeoJSON polygon', adding value beyond the annotations, which already indicate readOnlyHint and openWorldHint. However, it does not disclose further behavioral traits (e.g., underlying data source, rate limits, or computational cost). The annotations cover safety, so the description minimally supplements transparency.

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 consists of two concise sentences with no fluff. It front-loads the core purpose and uses plain language. Every sentence earns its place.

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?

Given the moderate complexity (4 required parameters, no nested objects, no output schema), the description is sufficiently complete. It explains the output format (GeoJSON polygon) and the use case. An output schema is not present, so the description partially compensates. It could mention default routing profile or data source, but overall it is adequate.

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?

The input schema provides 100% coverage with descriptions for all four parameters. The tool description does not add any additional meaning beyond what the schema already states. According to the rubric, high schema coverage yields a baseline of 3, and no extra value is provided, so the score is 3.

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 clearly states the tool's function: 'Get a reachability polygon showing everywhere reachable from a point within a given travel time.' This is a specific verb and resource, and it distinguishes the tool from siblings like get-directions and search-venues, which serve different purposes.

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?

The description includes a general use case ('useful for understanding how far someone can travel') but does not explicitly state when to use this tool versus alternatives. It lacks exclusion criteria or context for selecting this tool over siblings, which limits the agent's decision-making.

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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