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

With no annotations, the description carries the burden and does well: it scopes the effect to future mail, explicitly says existing Spam threads are untouched, and discloses the no-op/edge-case response ('answers that there was nothing to lift'). It does not mention permissions, reversibility, or what a successful response body looks like, leaving some behavioral surface uncovered.

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-loads the core effect in the first clause, then adds the two pieces of genuinely useful context (Spam threads unaffected, no-block case). The explanatory aside 'a block having always been about the mail still to come' is slightly rhetorical but justifies why the Spam exception exists.

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 one-parameter, non-destructive-in-appearance operation with no output schema and no annotations, the description covers what changes, what does not change, the workaround for the related need, and the no-op outcome. Nothing an agent needs to call it correctly appears to be 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?

Only one parameter and schema description coverage is 100%, with the schema itself directing the agent to list_blocked_senders for the address format. The description adds no syntax or formatting detail beyond that, so the schema does all the parameter work and 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 ('Lets an address write to the Inbox again') and immediately clarifies the effect ('their next message is filed like anybody else's'). It also differentiates itself from the obvious confusion case by naming file_conversation as the tool for moving already-blocked threads, so an agent can distinguish it from siblings without opening 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?

Clear about the situation it applies to — future mail from a blocked address — and explicitly redirects the adjacent need ('file_conversation with "inbox" is what brings one of them back') for threads already in Spam. It does not explicitly name list_blocked_senders as the discovery prerequisite in the description (that is only in the schema), so routing is slightly implicit.

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