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

Beyond the annotations (readOnlyHint=true, destructiveHint=false, openWorldHint=false), the description discloses real behavior: unmentioned attributes are preserved, ready-made designs are restricted to name/tagline/colour, and the response reports which changes applied and which could not. The only mild tension is that 'changes were applied' reads like a mutation while the annotations declare the tool read-only; it is best read as computing a new state, but the wording could be sharper.

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?

Three sentences, front-loaded with the trigger and followed by behavior, then exclusions — no filler. Slight cost in readability: 'Says which changes were applied and which this design can't do' packs two ideas into one clause and takes a second read.

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 a two-parameter tool with nested required objects and no output schema, the description covers trigger, partial-update semantics, per-design restrictions, and the fallback route. The one remaining gap is any cue about the shape of the result beyond 'which changes were applied', though the schema's state description carries the input contract.

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, and the description adds genuinely useful semantics on top: changes are partial (everything not mentioned is kept) and the permitted change set varies by design system (ready-made designs limited to name, tagline, colour). It does not explain the state parameter's provenance, but the schema field description already covers that.

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?

The description uses a specific verb and resource ('change a Webba design already shown') and enumerates the editable fields (name, tagline, colour, graphic, lettering, name placement). It explicitly distinguishes itself from the sibling find_designs, so an agent can separate the two without opening either 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?

It states the triggering condition ('when the person asks to change a design already shown') and gives explicit exclusions: 'Do not use this for a logo made elsewhere, or for a different business, which is find_designs.' It also names the fallback path (a builder alternative) when the edit is impossible.

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