block_sender

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

With no annotations, the description carries the full burden of behavioral disclosure. It does disclose the core mechanism (creating a filter) and the optional existing-mail trash behavior, but it omits important side effects such as the filter persisting after the call, the fact that the filter action is configurable (trash/archive/spam), and how to reverse the block (unblock_sender sibling exists but is not mentioned). A user cannot infer reversibility or what happens to incoming mail beyond 'block'.

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?

The description is exactly two sentences, front-loaded with the primary action and mechanism, then a concise optional behavior. Every word earns its place; there is no fluff, repetition, or unnecessary detail. This is an exemplary concise description.

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?

Given that there is no output schema and no annotations, the description only partially covers the needed context. It explains the mechanism and optional existing-mail trash, but it does not mention how to undo the block, when to prefer this over trash_emails, or that the filter action can be archive/spam. The schema covers parameters well, but the broader behavioral context is incomplete for a mutating tool.

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 parameters are fully described in the schema (account, sender, action, also_trash_existing). The description adds only a high-level context that the filter mirrors Gmail's Block button, which does not meaningfully elaborate on individual parameters. It provides no additional syntax or format details beyond what the schema already documents, so a baseline score of 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?

The description uses a specific verb 'Block a sender' and identifies the resource (sender) plus the mechanism ('by creating a Gmail filter'). It clearly distinguishes this from sibling tools like trash_emails (which only trashes selected messages) and unblock_sender (which removes a block). The reference to Gmail's native Block button makes the purpose instantly recognizable.

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?

The description implies usage context by equating the action to Gmail's Block button, but it does not explicitly state when to use this tool versus alternatives such as trash_emails or archive_emails. There are no exclusionary statements (e.g., 'use this when you want to prevent future mail; use trash_emails for one-off deletion'). The optional trash behavior is mentioned, but no alternatives are named.

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