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

The description explains the layout mechanics (start position + configurable spacing), which is useful context beyond the annotations. But annotations declare destructiveHint=true and readOnlyHint=false, and the description never says what that destruction means here — whether existing positions are overwritten, whether an overlapping block is displaced, or whether the move is undoable. With the safety profile already in annotations, this is adequate but leaves the mutation risk unexplained.

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, zero filler, with the what front-loaded and the routing constraint second. Every clause carries information an agent needs to choose between this tool and the auto-layout family.

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 7-parameter, fully schema-documented mutation with no output schema, the description covers purpose, scope, and the key alternative. What is missing is the consequence of the destructive mutation (displaced or overwritten blocks) and any indication of what the call returns or how a large cellIds list affects behavior.

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 layout, startX/startY, cellIds, spacing, gridColumns, and expectedProjectId are already documented, including defaults and enum meanings. The description restates the layout types and spacing but adds no new semantics such as how gridColumns interacts with grid or how expectedProjectId refusal behaves beyond the schema text. Baseline 3 applies when the schema carries the parameter detail.

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 (arranges), resource (several blocks), and the mechanism (row/column/grid from a start position with spacing). It also names the sibling auto_layout_canvas and the distinction (local few-block repositioning vs. whole-canvas tidying), so an agent can separate the two without opening a 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?

Explicitly bounds usage to 'LOCAL repositionings of a few blocks only' and routes the whole-canvas case to auto_layout_canvas with the reason (dedicated engines per kind). Both the when and the when-not are present, with the alternative named.

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