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

Annotations already state this is a non-read-only, non-destructive mutation. The description adds useful behavior: it is a partial update limited to provided fields and must happen before takeover. It still omits token authorization details, reversibility, non-idempotent behavior, and error conditions.

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?

It is a single short sentence with the state precondition and partial-update scope front-loaded. There is no redundant wording or filler.

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 nested mutation tool, the description covers the key state precondition and partial-update semantics. It remains thin on authentication token handling and failure behavior, although the schema documents id/token and annotations cover the basic safety profile.

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 67% and the nested changes object is partially documented. The description clarifies that only supplied fields inside changes are applied, which is meaningful, but it does not add detail for id, token, or the many nested fields beyond what the schema already says.

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 action, editing a draft, and adds the key scope that only supplied fields are changed. It does not name the sibling create_letter or explicitly say it updates an existing letter rather than a draft, so it falls short of full sibling differentiation.

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 'before takeover' implies this is for drafts that have not yet been claimed, and 'only given fields change' signals partial updates. However, it does not explicitly say when to use create_letter or get_letter instead, nor what happens if the draft was already taken over.

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