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

Annotations already declare readOnly/idempotent/non-destructive, but the description adds real behavioral context beyond them: fees post 7.5-13 days after purchase so today's fees do not exist yet, the store's own time zone is used, and the returned 'narrative' is pre-composed and must be read verbatim without recomputation. These are exactly the usage-critical traits an agent could not infer from structured fields.

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?

It is a long, dense passage but front-loads the core definition before the fine print about fee lag and verbatim reading. Nearly every clause earns its place, though it could be split for readability.

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?

With no output schema, the description compensates by naming the 'narrative' return field and instructing how to use it, plus explaining the data lag and time-zone scoping. For a zero-required-parameter read tool, nothing an agent needs to call 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?

Only one optional parameter and schema coverage is 100%, so the schema already documents marketplace_id fully. The description adds only a light implication that the brief itself names marketplace choices; baseline 3 is appropriate.

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 states a specific verb (how today is going) and resource (the connected Amazon seller account's daily brief), then enumerates the exact contents: units sold so far today, posted money, ad spend, attention items. This clearly distinguishes it from siblings like get_profit_summary or did_my_changes_work, which are analytical tools rather than a composed narrative brief.

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 gives explicit user-phrase triggers ('how did today go', 'what happened today', 'give me my morning brief'), which is strong when-to-use guidance. It does not name an alternative tool or state when not to use it, so it stops short of a 5.

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