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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), so the bar is lower, and the description still adds two useful facts beyond them: the rollup is computed live (freshness/consistency behavior) and the call requires the `emails:read` scope. It stops short of stating behavior on a missing or purged batch id.

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?

Two short sentences, zero filler, with the core action front-loaded and the scope constraint placed last where it reads as a prerequisite. Every clause carries information the agent cannot get from the name.

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?

An output schema exists, so return-shape explanation is unnecessary, and annotations plus the scope line cover safety and auth. What remains thin is disambiguation from sibling batch/campaign read tools and error behavior for an unknown id — minor for a one-parameter lookup.

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?

Single parameter with 100% schema description coverage — the schema already documents `id` as a `batch_…` string, so baseline 3 applies. The description adds no format, prefix, or lookup-by-alternative detail beyond what the schema provides.

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?

Specific verb+resource ("Retrieve a batch") plus a value-added qualifier ("live per-status rollup") that tells the agent what it gets back. It does not, however, differentiate itself from nearby siblings such as email_batches_cancel, email_send_batch, or email_get, leaving the agent to infer the boundary from the name alone.

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?

Usage is only implied: the read scope line establishes the permission context and "live per-status rollup" hints at polling a batch's progress, but there is no explicit when-to-use/when-not statement and no named alternative. Nothing actively misleads, but the agent must infer the routing.

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