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

With no annotations, the description carries the full burden and does: permission model (any writer), absence of revision bump, that baseRevision is unnecessary, that concurrent edits are unaffected, and that the response is the design's listing entry with the new title. This is exactly the behavioral context a caller cannot get 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-loaded with the action, then layered constraints; every sentence adds a distinct fact rather than repeating the name. It is prose-heavy with several chained clauses, but nothing is decorative.

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?

An output schema exists and the description still tells the agent what the reply is (listing entry with new title), which is a bonus rather than required. Remaining gap is the undocumented designId parameter and the absence of any error/conflict behavior; otherwise complete for a simple rename.

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 only 33% and only `token` has a schema description. The description clarifies the semantics of title (set at creation, cosmetic, not design content) and rules out baseRevision, but says nothing about designId format or any title constraints (length, uniqueness, trimming). Partial compensation for the coverage gap.

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+resource (rename a design's title) and immediately delimits it: the title is 'the one thing about a design nothing else could change' and is 'not part of any mutation'. This separates it from the mutation-oriented siblings (ui_builder_apply, ui_builder_replace_design_document) and from create/delete without the schema being opened.

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 concrete conditions: any writer of the design may rename it, baseRevision is not needed, and an in-flight edit is unaffected. It does not name a sibling alternative to use instead (e.g. when a title-like change should go through apply), so it stops short of explicit when-not routing.

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