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

Beyond the readOnlyHint/idempotent annotations, it discloses the economically important caveats: foreign-registrar domains are reported as unknown with reason foreign_registrar_pricing, never guessed or zeroed, and headroom is an upper bound when partial is true. It also reinforces 'cannot spend money,' which matters because a similarly named sibling (set_budget) does mutate.

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 definition, then the usage trigger, then caveats — a sound ordering. It is dense but nearly every clause carries informational weight; 'Read-only. Cannot spend money.' slightly overlaps the readOnlyHint annotation and is the one near-redundant line.

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-shape burden and discharges it by enumerating each reported figure and flagging the unknown-cost and partial-headroom semantics. For a single-parameter read tool, an agent has everything needed to call and interpret it.

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?

There is one parameter (project_id) with 0% schema description coverage. The description implies the parameter's role ('for one project') but never states the identifier's form or where to obtain it, so it only partially compensates for the undocumented schema.

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 description names a specific resource and operation ('the financial readout for one project') and enumerates exactly what the readout contains: budget, per-domain renewal costs, carry, unknown-cost count, headroom. It is clearly distinct from every sibling (list_projects, set_budget, quote_domain) because it is the only aggregate finance view.

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?

Usage is stated in intent terms: 'For questions about what a project costs to hold or how much budget is left.' That covers when to reach for it, but it never names the alternatives (set_budget for mutations, quote_domain for single-domain pricing) or exclusions, so routing is inferred rather than prescribed.

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