generate_keychain

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

With no annotations, the description carries the full burden and does a lot: it discloses a side effect (opens an interactive 3D stage panel / hosted browser link), an automatic mesh transformation (oversized meshes are decimated for the stage), and quota economics (3/month free, unlimited Pro). It omits persistence semantics (is the design saved/reopenable?), failure modes, and auth requirements, which keeps it short of a 5.

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?

Purpose is correctly front-loaded in the first sentence, but the inline 3D stage is explained twice (once in the opening parenthetical, again in a dedicated all-caps section), and the pricing/upgrade URL plus uppercase section headers add bulk without decision-relevant information.

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?

The output side is well covered (PNG preview plus interactive stage, decimation behavior), which matters given there is no output schema. The input side is not: 14 all-optional parameters with no annotations and only default-value schema text leave an agent guessing at what most fields mean and what a reasonable call looks like.

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 description coverage is 100%, so the baseline of 3 applies, but the schema entries only state defaults ('Default: "rectangle"', 'Default: 5.0') without explaining what front/back text, photo_mask, brief_id, color_overrides, or include_step actually control. The description says nothing about any of the 14 parameters, so it adds no meaning beyond the structured fields.

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?

Opens with a concrete verb+resource: 'Generate a 3D-printable keychain.' It also positions itself against named siblings (design_session, compile_scad) and against the family of other product generators, so an agent knows what it produces without opening the schema.

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?

The 'MAKE DOORS' paragraph routes the agent between design_session and compile_scad, which is real routing guidance. However, it never says when to pick generate_keychain over the many similar siblings (generate_nameplate, generate_coaster, generate_pet_tag, generate_fridge_magnet), and the compile_scad note reads as a fallback instruction rather than a selection rule for this tool.

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