Create an approved Sieve filter

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

Goes well beyond the annotations: it discloses that the Bridge backend always refuses before any form and leaves the token unused, that the operation adds exactly one filter and never replaces or removes one, and that it returns log_id. The destructiveHint=true annotation is conservative rather than contradicted, since the text clarifies the additive, non-removing semantics.

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 critical guidance is front-loaded, but the Bridge refusal is restated across three separate sentences ('always refuses and changes nothing', 'Proton Mail Bridge has no Sieve or filter interface', 'the refusal comes before any form'), which is redundant for a one-parameter tool.

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 single-token mutation tool with an output schema, the description covers preconditions, backend limitations, side effects, and the return value. Nothing an agent needs to decide whether and how to call it 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?

Schema coverage is 100% and the single token parameter is already documented, so the baseline is 3. The description adds real meaning beyond the schema: the token is single-use, must come from the approved preview, and is left unused if the call is refused.

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 ('Create the previewed Proton Sieve filter') and immediately ties it to the sibling that produces its input (preview_sieve_filter). An agent can distinguish it from preview_sieve_filter, preview_add_rule, and add_rule without opening any schema.

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?

Gives an explicit precondition ('only call after explicit approval of its preview'), an explicit when-not ('with Proton Mail Bridge ... it always refuses ... do not call it there'), and named alternatives (show the preview script, or preview_add_rule + add_rule). This is the full when/when-not/alternative triad.

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