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

With no annotations at all, the description carries the full burden and does meaningful work: it declares 'Read only' (safety profile absent from structured data) and discloses that the payout is computed at today's rate with no guaranteed rate and a shrinking pot. It omits whether wallet auth is required and what the response looks like.

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 short sentences, front-loaded with what the tool reports, followed by the decision context and the volatility caveat. No 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?

For a zero-parameter read tool with no output schema and no annotations, the description covers what is returned, the decision it supports, and the caveat that values are non-promised. It stops short of specifying auth requirements or the response shape, which is the remaining gap given no output schema exists.

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 the baseline of 4 applies; there is nothing for the description to disambiguate and it correctly adds no parameter talk.

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 resource (the home income pot) and the exact three quantities it returns: current ZENI balance, per-day payout, and days of runway at today's rate. It implicitly separates itself from apartment_quote/prepare_apartment_buy by framing itself as the pre-purchase check, but never names a sibling explicitly.

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?

'Check before buying an apartment' gives a concrete trigger condition, and 'the pot shrinks as it pays and no rate is promised' warns that the value is a snapshot. It does not name an alternative tool or state when not to call it, so it falls short of full when/when-not guidance.

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