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

Annotations already declare destructiveHint=true and readOnlyHint=false, and the description's 'Replace' corroborates that this overwrites the existing guide. It adds the 4,000-character ceiling, but does not disclose permission requirements or what happens to prior content on failure/excess length.

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?

A single dense sentence with the action front-loaded and the content constraint trailing. Every clause carries information, though the parenthetical about length slightly duplicates the schema's maxLength.

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 two-parameter mutation tool with no output schema and annotations covering the safety profile, the description says enough to call it correctly. It does not address error behavior, but that omission is minor at this complexity.

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 50%: model_id is documented in the schema, but the guide parameter has no description there. The description compensates by defining what the guide should contain (each category's meaning and its exceptions) and restating the length cap, adding genuine meaning beyond the schema.

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 ('Replace') and resource ('the model's labelling guide'), with scope detail about the guide's contents. An agent can distinguish this from the labelling_guide_get sibling by the get/set pairing, though the description never names the alternative explicitly.

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 phrase 'text the user agreed' implies this is used to persist a human-approved guide, giving implied workflow context. There is no explicit when-to-use/when-not or reference to labelling_guide_get, so usage must be inferred.

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