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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so the safety profile needs no restating. The description adds diagnostic value by naming what is returned and tying the call to a refused-save scenario. It does not state units (bytes vs. human-readable) or whether limits are per-account or per-plan.

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, no filler. The return contents are front-loaded and the usage triggers follow, so the agent gets both what and when immediately.

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 must carry the return-value burden, and it does list the four returned quantities. It falls just short of complete because units and limit scope are unstated, which matters for interpreting a quota response.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate beyond the schema's empty object. Baseline is 4 for a parameterless tool.

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 ('Returns') and enumerates the exact resource contents: storage used, document count, the limit on each, and max single-document size. No sibling in the list reports account-level quotas, so an agent can distinguish it from tp_list_documents or tp_get_document without opening the 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?

Gives two concrete triggers: when the user asks how much space is used or left, and when a save was refused for exceeding a limit. This is clear context for invocation. It stops short of a 5 because it names no alternative tool and no exclusion, though no sibling meaningfully overlaps here.

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