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

No annotations are supplied, so the description carries the full behavioral burden and delivers little: it says nothing about this being a read-only snapshot, about authentication requirements, data freshness, or caching. 'State' hints at a read, but that is inference rather than disclosure.

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?

A single short clause with the resource front-loaded and the returned fields listed compactly. No filler, but also no structure beyond the colon-delimited list.

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 is the only place return values can be described, and it names just three fields without units, formats, or whether the response includes additional vault metadata. For a parameterless read tool this is marginally adequate but leaves the agent guessing at the shape of the payload.

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?

Zero parameters, so the baseline is 4. There is nothing schema-side or description-side to reconcile, and the vacuous object schema means no parameter ambiguity exists.

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 the specific resource (perpetual vault state) and enumerates the three data points returned: redemption rate, total earnings, USD supply. That is enough for an agent to tell it apart from the market-data siblings (ohlcv, depth, ticker, trades). It stops short of a 5 because there is no explicit retrieval verb and the field list is descriptive rather than a statement of scope.

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?

No when-to-use guidance, no exclusions, and no reference to the sibling tools despite ten of them being available. The agent must infer that this is the vault-metrics endpoint; nothing says whether to call it for earnings analysis, redemption-rate monitoring, or both.

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