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

Annotations declare readOnly=false, destructive=false, idempotent=false; the description's 'Merge' wording is consistent and usefully discloses partial-update semantics (properties are merged, not replaced). It also explains the concurrency guard (expectedSpecVersion prevents stale writes), which annotations do not cover. It stops short of describing return behavior or auth requirements.

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 tight sentences, front-loaded with the core action and followed by the one critical precondition. Nothing redundant.

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 large discriminated-union mutation schema with no output schema, the description covers the essentials (merge semantics, version guard) but omits the layerType variant requirement and what the caller receives after a successful update. The rich nested paint description in the schema carries much of the remaining burden.

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?

Top-level schema description coverage is 0%, so the description must compensate. It explains the meaning and purpose of expectedSpecVersion (a version token guarding against stale writes), which the bare integer schema does not, and characterizes the input block as paint and display properties. It adds little for projectId and does not clarify the layerType discriminator, so compensation is partial.

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 gives a specific verb ('Merge') and resource ('a map layer's symbology') and enumerates the property classes touched (colours, ramps, opacity, stroke). This clearly distinguishes it from siblings like update_layer_label, set_layer_visibility, set_layer_filter, and set_layer_zoom_range.

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 'Merge ... into a map layer' phrasing implies it targets an existing layer's styling, and it states that expectedSpecVersion is required to prevent stale writes. However, it never says when to choose this over sibling mutators such as add_layer or duplicate_layer, and gives no exclusions.

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