Add Spam Blacklist Entry

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

Annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=false, so the safety profile is structured. The description adds real value beyond that: the 409 duplicate-error semantic, case-insensitive matching, wildcard support, and the important scope fact that sender lists are shared across all domains on the account.

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 clauses, front-loaded with the action and its effect, followed by the wildcard format, error semantics, and account-wide scope. No filler and nothing buried.

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?

With an output schema present, annotations covering safety, and full schema coverage, the description supplies everything else an agent needs for a 2-parameter mutation: duplicate handling, matching rules, and account-wide reach. Only a note on cross-domain authorization or immediate-effect timing would improve it further.

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%, so both `domain` and `entry` are already documented, including wildcard examples and patterns; the schema itself carries the heavy lifting. The description reiterates the wildcard example and adds the case-insensitivity note, but does not explain per-parameter syntax beyond what the schema states, so baseline 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?

States a specific verb and resource ('Adds an entry to the spam blacklist') and immediately gives the resulting behavior ('blacklisted senders are always treated as spam'). This is unmistakably distinct from the sibling remove_spam_blacklist_entry and get_spam_blacklist, so an agent can select it without opening a schema.

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 implied by the name and effect statement, and the 409 note tells the agent what happens on a duplicate, but there is no explicit when-to-use-vs-alternatives guidance (e.g., blacklist vs. whitelist conflict, or when to prefer update_spam_settings). Adequate but with a clear gap.

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