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

Annotations only carry destructiveHint=false and a title, so the description bears the transparency burden. It discloses a genuinely non-obvious behavior: applying a background to a TEXT entity 'would report success and change nothing' — a silent no-op failure mode. This is exactly the kind of behavioral insight an agent needs and cannot infer 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?

Two short sentences with zero filler. The primary purpose is front-loaded, and the critical MTEXT-only constraint follows immediately. Every clause earns its place.

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 4-parameter mutation tool with 100% schema coverage and an output schema, the description carries the essential context: the use case, the limitation, and the failure mode. It does not cover behavior for invalid handles or non-MTEXT/non-TEXT entities, but the 'MTEXT only' framing plus the TEXT warning cover the realistic failure cases sufficiently.

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%, with color, scale, handle, and enabled all documented in the input schema itself. The description adds no parameter-level detail beyond the schema, so the baseline of 3 applies.

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 states a specific verb and resource — 'Mask what is behind an MTEXT' — and explains the purpose (keeping text readable over hatch or geometry). It also distinguishes this tool from anything targeting TEXT entities, which uniquely identifies its scope among siblings like entity_create_mtext and entity_create_wipeout.

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 description gives clear context for when to use the tool (when MTEXT needs readability over hatch/geometry) and an explicit exclusion: TEXT has no background-fill attribute, so using it on TEXT would silently do nothing. It does not name an alternative tool (e.g., entity_create_wipeout) for masking behind generic geometry, so it stops short of a full 5.

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