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Umbra open SAR archive

by io.github.reesehammer
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change_composite

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Composite 2-3 passes of one site into a change image.

Pass the STAC URLs of two or three acquisitions of the *same* site in time
order. Colors encode change: bright green = signal appeared after the first
date, magenta = signal vanished, grey = unchanged. Refuses to mix
polarizations (HH vs VV are not comparable). Returns the image block plus a
caption naming the color semantics and attribution -- and, when a pass carries
no polarization metadata so same-polarization could not be *verified*, a
structured caution text block naming that gap.

Input Schema

NameRequiredDescriptionDefault
dbNo
urlsYes
assetNoGEC
max_sizeNo

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A4.7/5.0
Behavior5/5

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

The description goes far beyond the single annotation, detailing the specific color encoding rules, the exact components of the output (image block, caption, caution block), and conditional behavior (the caution text appears when polarization cannot be verified).

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 highly dense, front-loaded with the main function, and efficiently packs technical constraints and output details into coherent sentences.

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

Completeness5/5

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

Given the high complexity of the transformation, the description is exhaustive. It explains the input requirements, the internal logic (color encoding), and the exact structure of the output result.

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?

Since schema coverage is 0%, the description should define all parameters. It only provides semantic value for the core 'urls' parameter, failing to define the purpose of 'db', 'asset', or 'max_size'.

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 creates a 'change image' by combining 2-3 passes of a single site, which distinguishes it as a specialized composite generation function.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It provides explicit requirements for proper usage: the STAC URLs must be for the same site and provided in time order. It also gives a critical exclusion regarding polarization.

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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