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

Beyond the readOnly/idempotent annotations, the description discloses real behavioral consequences: matching mail is 'passed by in the first look and in every later read, and nothing of it is kept', and a domain entry covers its subdomains. That is exactly the kind of operational impact an agent cannot infer from annotations or schema.

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?

Front-loaded with the core definition, then behavior, then the sibling distinction — every sentence earns its place. The first clause is dense (em-dash examples, nested relative clause) and would benefit from one fewer aside, but nothing is wasted.

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 zero parameters, no output schema, and read-only annotations, the remaining burden is explaining what the entries are and what the list does — both covered. Nothing an agent needs to call or interpret this tool is missing.

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?

The tool takes no parameters, so the baseline is 4 and the description has no parameter ground to cover. Nothing here misrepresents the (empty) input contract.

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?

Names the exact resource (the list of addresses/domains Tommo won't read mail from) and states what it is not by naming the sibling list_blocked_senders. It also specifies entry contents (address vs domain, who added, when), so an agent knows precisely what this returns without opening anything else.

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 closing contrast ('Not the blocked senders (list_blocked_senders), which are spam') gives a clear condition for choosing this tool over its nearest sibling, and the ignore-list semantics imply when to inspect it. It stops short of explicitly routing to add_to_the_mail_tommo_wont_read / remove_from_the_mail_tommo_wont_read for mutation, which is the only gap.

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