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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=true, so safety and repeatability are covered. The description adds genuinely useful behavior not in the annotations: `data` is paginated while `selection` is returned as the full rule config, and it discloses that a sibling add/set call exists for the write side. It says nothing about auth scope, rate limits, or ordering, so it stays modest rather than rich.

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 blocking requirement is front-loaded in the first words, which is exactly right for a tool that fails without signature_id. The rest is dense but each clause carries information (what sources mean, what selection contains, pagination vs. full-config behavior). Slightly long for a read-only list endpoint, but not padded.

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 read-only, idempotent list tool with a full annotation profile, an output schema, and 100% schema coverage, the definition covers the only real failure mode (missing signature_id) and how to recover from it. It even previews the shape of the returned rule config, so nothing an agent needs to invoke it correctly 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 description coverage is 100%, so page, limit, context, max_pages, signature_id and auto_paginate are all already documented, which sets the baseline at 3. The description's signature_id note (a signature template UUID from list_signatures) largely restates the schema, and it never discusses auto_paginate/max_pages interaction; its extra detail (sources values, selection contents) explains the return payload rather than the inputs.

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 (list the emails a signature is assigned to) and then details the payload shape (sources explanations plus the selection rule config). That scope is clearly distinct from list_signatures, which it names, and from the sibling mutators add/remove/set_signature_recipient*. An agent can pick this tool without opening the 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 the prerequisite explicitly (REQUIRES signature_id, a template UUID), rules out the wrong assumption ("there is no workspace-wide form of this tool"), and routes the agent to the alternative that produces the needed id (list_signatures, pass an `id` from it). That is explicit when-to-use and how-to-unblock guidance.

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