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

Annotations already cover the safety profile (read-only, closed-world, non-destructive), and the description adds genuinely useful behavior beyond them: newest-first ordering, an unknown-domain error, and metering semantics ('once per store per month'). These are the details an agent needs to decide whether to spend a call.

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 payload description is front-loaded and every clause adds information (fields, ordering, follow-up tool, error, metering). It is slightly dense/run-on in the opening sentence, but nothing is wasted.

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?

There is no output schema, so the description carries the return-value burden and does so by listing the returned fields and their ordering. Combined with the error and cost notes, an agent has everything needed to call it correctly.

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 domain normalization and the limit default/max are already documented in the schema. The description adds no parameter-level syntax or constraints beyond that, so the 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+resource (marketing/newsletter emails captured from a store) and enumerates exactly what comes back: subject, sender, snippet, discount codes, received date, plus cadence. It is clearly distinguishable from get_store_email (single email body by id) and get_store.

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?

It routes the agent to the sibling for a follow-up need ('Each email's full body is available from get_store_email by id') and flags failure conditions ('Returns an error if the domain is unknown'). It does not explicitly frame when a different tool should be used instead of this one, but the context is clear.

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