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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint=false and destructiveHint=false, and 'Reads only' merely restates them. What the description does add beyond annotations is return-shape behavior: each quota comes with its limit, what counts toward it, when a monthly one resets, plus anything paused by a downgrade — valuable since there is no output schema. It does not cover failure modes, permissions, or how 'PLAN NOTICE' appears in responses.

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?

Usage triggers are front-loaded after a single dense scope sentence, and the closing 'Reads only' is a compact safety tag. The first sentence is long and list-heavy, which slightly slows parsing, but no sentence is filler.

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 carries the return-value burden and does so well by enumerating the counters, their limits, reset timing, and downgrade pauses. Remaining gaps are minor: it does not say how a project lookup degrades the account-level view or what an invalid project name yields.

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% and the single parameter is fully documented there, so the baseline is 3. The description's 'Name a project to see how many people it may have instead' essentially duplicates the schema text rather than adding new semantics (e.g., name-vs-id ambiguity or behavior when the project is unknown).

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 opening clause states a specific verb and resource: what the account's RelayLink plan allows and how much of each quota is used, then enumerates the exact counters (memories, notebook items, projects, tracked items, forwarding addresses, forwarded messages, new conversations). It is clearly distinct from siblings like upgrade_plan (changing plans) and project_list (listing projects), so an agent can route between them without opening a schema.

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 triggers: when the user asks about their plan, limits, or what is left, and after a refusal or a PLAN NOTICE, before suggesting what to delete or change. It also states the one branch condition — name a project to see that project's people allowance instead of the account's — so the agent knows when the optional parameter changes the answer.

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