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

Annotations already cover the safety profile (readOnlyHint=false, destructiveHint=false, openWorldHint=true), and the description adds real context on top: no portfolio-level budget cap and no extra authorization beyond campaign scope. It omits the two-step preview/confirm write flow that the confirm_id parameter implies, which an agent would only learn from the schema.

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 sentences with the purpose front-loaded and the budget-cap caveat placed immediately after. Denseness in the parentheticals is slightly high 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?

For a mutation tool with no output schema, the description never says what is returned (e.g., the new portfolio ID needed for campaign assignment) and does not surface the preview-then-confirm requirement. Annotations cover the mutation safety profile, but these operational gaps remain.

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 67% (account_id and confirm_id documented, the required nested portfolio object not), and the description adds no parameter-level detail such as what profile_id means at the portfolio level. The schema does most of the work, so the baseline 3 holds.

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 ("Create an Amazon Ads portfolio") plus its function ("to group campaigns"), which is enough to separate it from the list/update siblings that operate on campaigns. It does not explicitly name a sibling such as ads_list_portfolios, so it stops just short of a 5.

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 implied rather than stated: the agent can infer it should call this before assigning campaigns to a portfolio, and "campaigns can then be assigned to it" signals sequencing. There is no explicit when-not guidance and no named alternative for inspecting existing portfolios.

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