Ollama's Go renderer drops the definition of any tool parameter named type or description

The filter lives in one Go function. Ollama renders gemma4 prompts in Go, in model/renderers/gemma4.go, and checks that renderer against the model's reference Jinja template committed under model/renderers/testdata/ ^[17]. In the template, the format_parameters macro takes filter_keys=false and skips the five schema keywords only when a caller asks; the macro is called four times, three of the calls pass nothing, and exactly one filters ^[6][18]. The Go equivalent, writeSchemaProperties, filters unconditionally and serves all four call sites ^[6].

urgent_A7 is a string that appears nowhere in the prompt except inside that parameter's definition ^[14]. Named kind, the parameter came back as urgent_A7 in both runs ^[13]. Named description, the same definition produced "description": "Urgent water leak.", a sentence built out of the user message, which was Open an urgent ticket titled 'Water leak' ^[13][11]. The only thing that changed between those requests was the name of the second parameter ^[12].

The two model sizes fail differently. According to the dev.to writeup, a bigger model declines to guess and a smaller one guesses, and both behaviours come from the same missing text ^[23]. Two runs each at temperature 0 is a determinism check, not a sample of a population ^[12]. For those outputs to describe your service you need a gemma4 model, a renderer carrying the unconditional filter, and a required parameter whose name is one of the five ^[26][9].

The reporter's numbers describe a debugging session, not the model: 35 schema-validation failures over 14 attempts is 2.5 rejected outputs per attempt, and one ticket created in 14 attempts is about 7 percent ^[24][25]. Every one of those failures named a required parameter called description ^[15]. Renaming the parameter is what showed the model had never seen it ^[27].

JSON Schema has no rule against property names that happen to be schema keywords. Inside properties they sit in a different namespace, and every validator handles them correctly ^[19]. So a validating handler and this renderer read the same document differently. A handler that does not validate stores "type": "urgent" as a priority code, and you find out later ^[22]. The names are ordinary ones: type is the most natural name for a categorical field, and description is what the free-text field on a ticket is called ^[28].

Restoring the dropped argument takes twelve lines, and the same request then returns urgent_A7 ^[7]. Until that lands, the fix available to you is the parameter's name ^[8]. Ollama has no debug setting that prints the rendered prompt, so the declaration the model actually receives can be seen only by reading the renderer or running it ^[16].