block_sender

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

With no annotations, the description carries the full behavioral burden and does well: it discloses the underlying mechanism (inbox rule to Deleted Items), scope (future mail only), and reversal path. It omits edge behavior such as what happens with zero inputs, permission/auth requirements, and whether rule creation is idempotent.

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?

Four short sentences, front-loaded with the core action and mechanism, followed by input semantics, scope limitation, and undo guidance. Every sentence adds distinct value with no repetition.

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 two-parameter mutation tool with no annotations or output schema, the description covers mechanism, input matching rules, scope boundary, sibling alternative, and undo path. It is nearly complete, though it does not address empty input or return/error behavior.

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 100%, so the baseline is 3, but the description adds meaningful semantics: addresses use exact match while domains match any sender at that domain, and either or both may be supplied. This goes beyond the minimal schema descriptions.

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: blocking senders by creating an inbox rule that moves future mail to Deleted Items. It distinguishes itself from siblings by naming delete_message for existing mail and delete_rule for undo, so an agent can select it without inspecting other schemas.

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?

Explicitly explains when to use this tool (future sender blocking) versus delete_message (already-received mail) and how to undo via delete_rule. It also clarifies accepted inputs: addresses and/or domains.

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