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

Goes far beyond the annotations (readOnlyHint=false, destructiveHint=false): it discloses that from an API key or assistant nothing is sent, that seats = members plus open invitations and are plan-limited, and exactly what the response contains (free seats, or an upgrade plan with price and checkout link, plus the dashboard link and Settings > Team steps). That is exactly the non-obvious behavior an agent needs before calling.

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?

Front-loaded with the core action, which is good, but it is a single dense run-on paragraph with nested parentheses and semicolon-separated role definitions that is hard to scan. Most content earns its place, yet the role glossary and the fallback-response explanation would be far more usable as separate sentences or bullets.

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, and the description compensates by spelling out the return payload in both branches (seats available vs. upgrade plan with price and checkout link) plus the manual steps. For a three-parameter mutation-intent tool with full schema coverage, nothing an agent needs in order to call or interpret the result 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?

Schema coverage is 100%, so the baseline is 3, but the description adds real meaning the schema lacks: it defines what each of the five enum roles can actually do and states the implicit constraint that admins cannot be brand-limited while the other four roles can. It restates brand_ids' omit-for-every-brand behavior already in the schema, keeping it just short of a 5.

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?

Names a specific verb and resource ('Invites a person by email to work in this PostWire workspace') and enumerates the role model, so it is distinguishable from all siblings. The one wrinkle is that the headline verb overpromises: when called from an AI assistant nothing is actually sent, which the description later discloses, so the agent must reconcile the name with the real effect.

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?

Gives clear context for use: role selection, brand scoping rules ('Editors, contributors, approvers and viewers can be limited to some brands'), and the crucial constraint that only a signed-in dashboard user can actually add people. No sibling alternative exists to route against, and there is no explicit when-not guidance, but the practical usage envelope is unambiguous.

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