Update HUD

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

Annotations declare readOnlyHint=false and idempotentHint=true but cannot convey that the write is confined to ephemeral UI state; the description supplies exactly that ('does not change the document'), which is the key behavioral nuance. It also explains how delta renders (+/-) and that the note should be short. It stops short of saying whether the badge persists across sessions or what happens to fields that are omitted.

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?

Two sentences, front-loaded with the action and target, then the parameter meanings, then the safety caveat. No filler and nothing repeated from the schema.

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 three-optional-parameter UI tool with annotations and no output schema, most of what an agent needs is present. The notable gap is what happens when only some of score/delta/note are passed — whether omitted fields are preserved or cleared — which matters for correct incremental use.

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?

With 0% schema description coverage, the description carries the full burden and does define all three parameters: score as a 0–100 design quality estimate, delta as change since the last update rendered as +/-, note as a short message. It adds meaning the schema cannot, though it doesn't clarify partial-update semantics for the optional parameters.

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 and resource — 'Update the small heads-up badge in the editor top bar' — and enumerates exactly what it sets (score, delta, note). This clearly separates it from document-mutating siblings like mutate_canvas and from read-only siblings like canvas_status.

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 line 'Purely informational for the user; it does not change the document' implicitly steers the agent away from using this for real edits, but no sibling is named as the alternative for actual changes. There is also no guidance on when to update the HUD, how often, or whether omitting fields is acceptable.

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