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

Annotations already declare readOnly/idempotent/non-destructive, so safety is covered; the description goes well beyond that by disclosing data provenance (figures are only meaningful when you check both `currency` and `status_currency`), the rollup-time semantics of `spend_cents`/`projected_cents`, and an explicit warning never to quote the values as dollars blindly. That is exactly the behavioral context an agent cannot get from structured fields.

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?

Three sentences, front-loaded with what the tool returns before the caveats. The long currency sentence is dense but every clause carries a distinct, non-redundant constraint (denomination, base-currency divergence, rollup provenance), and 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?

There is no output schema, so the description carries the full burden of describing the return payload, and it does so by naming the status fields, the two currency fields, and the rollup caveat that governs their interpretation. For a zero-parameter, read-only list tool this leaves nothing material unexplained.

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 schema has zero parameters, which sets a baseline of 4. The description's discussion of `currency`, `amount_cents`, `spend_cents`, and `projected_cents` concerns response fields rather than inputs, so it adds nothing to parameter semantics but loses nothing either.

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 and resource (list this account's spend budgets) and enumerates the scope of the payload (current-cycle status: spend so far, projected total, ok/warning/exceeded, forecast). It also anchors the tool to a concrete upstream endpoint (GET /api/accounts/:accountId/budgets), so the agent knows exactly what domain object is being returned.

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 contrasts this tool with the sibling cost tools by warning that budget figures are NOT converted to the USD base those tools return, which gives the agent a selection signal. However, it never states a positive 'use this when...' condition or names a competing sibling tool for a specific budget question, so the routing guidance is implicit rather than explicit.

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