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turkenberg

MCAP MCP Server

by turkenberg

load_recording

Decode MCAP recordings into DuckDB for SQL queries. Filter by topics and time range to reduce load time.

Instructions

Decode an MCAP file and load its data into DuckDB for SQL querying. This decodes all messages and may take seconds to tens of seconds depending on file size. You must call this before running queries. For large files, use 'topics' to load only the topics you need and 'start_time'/'end_time' to narrow the time window — this significantly reduces both load time and memory usage. Set an alias for multi-recording comparison.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
fileYes
aliasNo
topicsNo
end_timeNo
downsampleNo
start_timeNo

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
resultYes
Behavior4/5

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

Describes that decoding all messages may take seconds to tens of seconds, and that filtering reduces load time and memory usage. Since no annotations provided, the description adequately covers behavioral traits.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

A single paragraph with clear, front-loaded main purpose. Each sentence adds value, though could be slightly more structured (e.g., bullet points). No wasted words.

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 tool has 6 parameters and an output schema, the description covers the load process, prerequisites, performance considerations, and usage of optional parameters. Sufficient for a complex tool without needing to explain return values.

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

Parameters4/5

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

With 0% schema coverage, the description explains the purpose of 'file', 'topics', 'start_time', 'end_time', and 'alias', covering most parameters. Only 'downsample' is not described. Adds significant value beyond the schema.

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?

States specifically that it decodes an MCAP file and loads into DuckDB for SQL querying. Clearly distinguishes from sibling tools like 'query' and 'list_recordings'.

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?

Explicitly says 'You must call this before running queries' and provides tips for large files (use topics, start_time/end_time to filter) and setting alias for multi-recording comparison, effectively guiding when and how to use.

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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