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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds genuinely non-obvious domain behavior: that the returned balance is informational only and does not confer spending authority, which prevents a costly misuse. It omits return shape and whether the balance is global or per-project.

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 short sentences, front-loaded with the core action, then the constraint. Each sentence adds distinct information (what it reads, what it is not, where spending actually originates). Minimal waste, though the second and third sentences could be merged without loss.

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?

This is a simple read with one optional parameter and no output schema, so the bar is modest, but the description leaves the scoping question unanswered. An agent cannot determine from the definition what a call without project_id returns, which matters for a balance check whose result gates spending decisions.

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, so the description carries the full burden of explaining it. The description never mentions project_id, its optionality, or what scope is used when it is omitted, so an agent cannot tell whether the call returns a global balance or a project-specific one.

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?

"Reads the balance available for work" gives a specific verb (read) and resource (balance), which matches the capacity family of siblings. It stops short of distinguishing itself explicitly from get_capacity_quote, get_capacity_entitlements, or get_capacity_catalog, so an agent must infer which capacity-read tool to pick from the name alone.

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?

The description supplies a clear when-NOT: a balance is not permission to spend, and paid work requires an approved quote. However, it never states when to call this tool (e.g., before quoting, before claiming free capacity) and does not name the sibling tools that own the quote/authorize flow, leaving the routing to inference.

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