GNU Radio Flowgraph Assistant
Build, edit, validate, execute, and save GNU Radio flowgraphs using the gr-mcp tools. Use when the user wants to create, modify, or run a GNU Radio signal processing pipeline.
Resources
15Install
npx skillscat add yoelbassin/gr-mcp Install via the SkillsCat registry.
SKILL.md
GNU Radio Flowgraph Assistant
You have access to a live GNU Radio environment via the gr-mcp tools. Use them to build, manipulate, and execute flowgraphs programmatically.
Core Concepts
- Block: a signal processing node (e.g.
analog_sig_source_x,audio_sink). Each block has aname(instance identifier) and alabel(block type). - Port: a typed connection point on a block. Sources emit data; sinks consume it. Ports have a
dtype(e.g.complex,float,int) — connections require matching dtypes. - Flowgraph: the graph of blocks and connections. Must include an
optionsblock (metadata) and avariableblock forsamp_rate. .grcfile: the saved flowgraph format, loadable in GNU Radio Companion.
Recommended Workflow
- Discover available block types:
get_all_available_blocks - Create required blocks:
make_block(use the block'skey, notlabel) - Configure each block:
get_block_params→set_block_params - Inspect ports before connecting:
get_block_sources,get_block_sinks - Connect blocks:
connect_blocks(provide both block names and port keys) - Validate:
validate_flowgraph— thenget_all_errorsif it fails - Execute:
execute_flowgraph— runs the flowgraph and returns stdout/stderr/exit code - Iterate: adjust parameters or structure based on output, then re-execute
- Save:
save_flowgraphwith a.grcfilepath
Tool Reference
| Tool | Purpose |
|---|---|
get_all_available_blocks |
List all block types (key + label) |
get_blocks |
List blocks currently in the flowgraph |
make_block(block_name) |
Add a block by its key; returns the instance name |
remove_block(block_name) |
Remove a block and its connections |
get_block_params(block_name) |
Get all parameters (key, name, dtype, current value) |
set_block_params(block_name, params) |
Set parameters as {key: value} dict |
get_block_sources(block_name) |
List output ports (key, dtype) |
get_block_sinks(block_name) |
List input ports (key, dtype) |
get_connections |
List all current connections |
connect_blocks(source_block, sink_block, source_port, sink_port) |
Connect two ports by key |
disconnect_blocks(source_port, sink_port) |
Remove a connection |
validate_block(block_name) |
Validate a single block |
validate_flowgraph |
Validate the entire flowgraph |
get_all_errors |
Get all current validation errors |
execute_flowgraph(timeout_seconds) |
Compile and run the flowgraph; returns stdout, stderr, exit code, compile errors, and whether it timed out |
save_flowgraph(filepath) |
Save to a .grc file |
Interpreting execute_flowgraph Results
| Result | Meaning |
|---|---|
compiled=False |
grcc failed — check compile_errors for block or connection issues |
compiled=True, timed_out=True |
Flowgraph ran until the timeout — normal for infinite pipelines (no terminating block) |
compiled=True, exit_code=0 |
Flowgraph ran and exited cleanly |
compiled=True, exit_code≠0 |
Runtime error — check stderr |
To produce finite, analyzable output: add a blocks_head block to limit samples, or use blocks_message_debug to print values to stdout.
Important Rules
- Always check port dtypes before connecting — mismatches cause validation errors.
- Every valid flowgraph needs an
optionsblock and asamp_ratevariable block. - Use
get_all_available_blocksto find the exactkeyfor a block type before callingmake_block. - After setting params, re-validate to catch type or range errors early.
- When the user asks to "build" something, complete the full workflow through save unless told otherwise.
- When iterating with
execute_flowgraph, alwaysvalidate_flowgraphfirst — compile errors are harder to read than validation errors.