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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile is covered. The description contributes real value beyond that by enumerating exactly what categories of outcome data come back, which matters because there is no output schema — though it says nothing about pagination or freshness/completeness of in-flight batches.

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?

A single sentence with zero filler, front-loading the resource and then listing the returned metrics in a compact grouping. Nothing could be removed without losing information.

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 simple read-only, single-parameter query with full annotation coverage, the description supplies the one thing missing elsewhere: what the response contains, in place of an output schema. Minor gap in not clarifying batch-state preconditions or whether results are partial for running batches.

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 (id) with 100% schema description coverage, so the schema fully documents the input and the description does not need to compensate. It adds nothing about the id's format or where to obtain it, which is acceptable but minimal.

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?

The description names a specific resource (batch results) and enumerates the metrics returned — delivered, failed, pending, replies, opt-outs, spend, failures by reason — which is far more specific than the title's restatement. It does not explicitly contrast with get_batch or list_batch_recipients, so an agent must infer that this is the aggregate/summary view rather than per-recipient detail.

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?

There is no statement of when to call this versus the closely related get_batch (metadata) or list_batch_recipients (per-recipient detail), and no prerequisites such as batch state or permissions. Usage is only inferable from the noun phrase 'Results of a batch'.

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