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

Annotations already declare destructiveHint=true, idempotentHint=true and readOnlyHint=false; the description adds real value beyond that by disclosing PATCH semantics, the pause-via-enabled=false behavior, inheritance of create rules, and an environment restriction. It does not spell out why the operation is flagged destructive, but nothing contradicts the hints.

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?

Three short sentences, zero filler, with the most decision-relevant fact (send only the fields to change) front-loaded. The parenthetical environment caveat is placed last where it belongs.

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 12-parameter mutation with no output schema, the description does most of the work by offloading field validation to create_auto_reply and explaining the patch contract. The remaining gap is that it never says where rule_id comes from (list_auto_replies) and does not indicate what the call returns.

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 83%, so the schema already documents nearly all 12 parameters. The description adds the meaningful partial-update convention and the semantics of enabled=false, but says nothing about the undocumented rule_id or about omitting versus nulling fields (message and link_url accept null). Baseline 3 is appropriate.

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 and resource ('Changes a rule') and immediately clarifies that it is a partial-update operation ('send only the fields to change'). A reader can distinguish it from create_auto_reply and delete_auto_reply, though the term 'rule' rather than 'auto-reply' requires the title/sibling list to disambiguate.

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?

Gives concrete usage conditions: send only changed fields, enabled=false pauses rather than deletes, and the create_auto_reply field rules carry over. It also flags an exclusion ('Not available in an unclaimed sandbox'). It does not explicitly route to delete_auto_reply when removal is intended, but the pause-versus-delete hint covers the main confusion.

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