Set a fixture attribute

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

No annotations exist, so the description carries the full burden and does: it discloses that ClearSelection is sent and the selection changes, that previously selected fixtures are untouched unless add_to_selection is true, and that programmer values are never cleared. It also spells out the pre-check/verify pipeline and the mismatch-is-not-success rule, which an agent could not infer from the schema.

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

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

Front-loads the core purpose in the first sentence and then walks through targeting, side effects, and verification in a logical order. Dense but each sentence carries information; the final serialisation note and a few packed clauses edge it just below maximum readability.

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

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

For an 8-parameter mutation tool with no annotations and no output schema, the description covers what an agent needs: how to target, what mutations occur to the selection and programmer, how failures are surfaced (pre-check failure, verification mismatch), and version constraints for verify. Nothing critical to correct invocation is missing.

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

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

Schema coverage is 100%, so the baseline is 3, but the description adds real meaning: the effect of omitting `unit` (interpreted by the user profile's readout), the selection side effect of `fixtures`, and the dependency of `check_attributes` on target size. These are behavioural couplings the per-property schema text only partially conveys.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb ('Set'), a bounded resource ('one attribute ... to an absolute value in the programmer'), and gives concrete examples (Dimmer, Pan, Zoom, ColorRGB_R). It also names the underlying command sent, so the mechanism is unambiguous. It never explicitly differentiates from nearby siblings that also write values (gma3_set_color, gma3_set_position, gma3_set_property), so it lands at clear-but-not-differentiating.

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

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

Gives clear operating context: the target must be explicit via `fixtures` OR `use_selection: true`, when the pre-check applies (small explicit targets, <=8 fixtures), when verification runs, and that the operation is serialised against this server's other mutations. It stops short of saying when to prefer this over gma3_set_color/gma3_set_position or gma3_command, so no explicit alternative routing.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.