Create Forwarder

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

The annotations already declare the mutating, non-idempotent, non-destructive profile, but the description adds a genuinely non-obvious side effect: forwarding to Gmail/Yahoo/AOL automatically enables Expert Spam Filtering for the domain. It also explains the semantic effect of the special destination values, which is real behavioral information beyond the safety hints. It does not cover duplicate-alias handling or failure modes.

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 compact sentences, front-loading the core action before the special-destination semantics and the domain-wide side effect. Nothing is padded or repeated unnecessarily for a tool of this scope.

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?

An output schema exists, so return values need not be explained, and the annotations carry the safety profile; the description fills its remaining duty by disclosing the automatic spam-filtering side effect. The only material gap is preconditions and duplicate/error behavior for an alias that already has a forwarder.

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 the alias/domain formats and the :blackhole:/:fail: constants already documented in the schema itself, so the baseline is 3. The description re-states the special destination meanings in behavioral terms but adds no syntax, format, or constraint information the schema lacks.

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 opens with a specific verb and resource ('Creates an email forwarder for an alias on a domain'), which is enough for an agent to distinguish it from sibling tools such as create_email_account or delete_forwarder. It stops short of explicitly naming the sibling it differs from, so it lands just below the top score.

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?

Usage is only implied by the purpose statement; there is no explicit when-to-use versus when-to-use-delete_forwarder or create_email_account guidance. It also omits prerequisites, such as the domain already existing on the account, or what happens when a forwarder for that alias already exists.

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