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

Annotations already declare readOnlyHint=false, destructiveHint=false, and openWorldHint=false, so the safety profile is covered externally. The description adds nothing beyond that: no disclosure of duplicate handling, whether blocking is idempotent, what happens to already-blocked addresses, or the effect on workspace scope.

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?

Very short and front-loaded, but the first clause ('Add to Blocklist') is a pure restatement of the name/title and consumes roughly half the text, leaving only one short functional clause.

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?

The tool is simple, has full schema coverage, annotations, and an output schema, so the description needs little. Still, for a mutation it omits return behavior signals like whether blocked entries appear immediately and how duplicates are reported, leaving minor gaps.

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 parameters are already documented, including that the emails array accepts domains. The description's 'emails and/or domains' phrasing merely restates the schema rather than adding format or constraint details, so the 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 (add) and resource (emails/domains to the blocklist), so the operation is unambiguous. However, it does not distinguish itself from close siblings like remove_from_blocklist, check_blocklist, get_blocklist, or delete_blocklist_entry — the agent must infer the difference from names alone.

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?

No when-to-use guidance is given: nothing about when to block versus check or remove, and no mention of prerequisites such as whether the sender must exist first. Usage is only implied by the tool name.

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