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

The description goes well beyond the annotations by explaining response behavior (CURRENT CARRY and HEADROOM are precomputed), edge-case semantics (unknown renewal prices count as unknown, never zero, making headroom an upper bound), and the important fact that budget affects recommendations but never prices. This is rich, non-obvious behavioral detail.

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?

The description is front-loaded with the usage trigger and contains valuable details, but several sentences repeat the same point: 'It records their ceiling', 'Records a number you chose', and 'Cannot spend money and cannot buy anything' are redundant. The all-caps pricing sentence also adds noise despite being important.

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?

Despite having no output schema, the description explains what the response contains (CURRENT CARRY and HEADROOM) and the special partial-headroom case. It also addresses pricing misconceptions. Missing only minor details like overwrite behavior, but with idempotentHint=true and the rich narrative, this is adequate for correct invocation.

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?

Schema description coverage is 0%, so the description must carry the weight. It does this by explaining that period is monthly or yearly, amount is expressed in cents, and the target is a project. It does not give detailed constraints or ranges, but it meaningfully maps to all three parameters.

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 uses specific verbs and resources: it records a spending limit for a project and never authorizes a purchase. It clearly differentiates itself from purchase-related actions and from pricing tools by stating it cannot spend or buy anything and that prices are unaffected by budget.

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 gives an explicit trigger: 'Use this when the user states a spending limit for a project.' It also provides exclusions ('never authorises a purchase', 'Cannot spend money and cannot buy anything'), but does not name alternative sibling tools or explicitly contrast with them.

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