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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the tool is known to be safe. The description adds useful behavioral context beyond that: it computes a 6-month EMA baseline, overlays recurrences, and conditionally runs an LLM-adjusted refinement when refine=true. It stops short of describing output shape or cost/latency implications, so it is not a 5.

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 compact sentences with no filler. The core action is front-loaded, followed by the return composition and the refine guardrail. Every sentence earns its place.

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 read-only forecast tool with no output schema, the description explains what the response contains and the two modes of operation. The main gaps are the unspecified output format/currency and lack of explicit sibling routing, but the schema covers parameters and annotations cover safety, so it is reasonably complete.

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 100%, so the baseline is 3. The description adds value for refine by stating its default and the explicit-user-request condition, which is not fully captured by the schema alone. yearMonth and householdId rely on their schema descriptions, which are already adequate.

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 a specific verb and resource: 'Produce a per-category spend projection for :yearMonth.' It also specifies the output composition (EMA baseline + recurrence overlay + optional LLM refinement), which clearly distinguishes it from generic siblings like generate_report and list_insights.

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 implies when to use the tool: when a monthly per-category spending projection is needed. It also gives a clear conditional rule for refine ('only enable when the user explicitly asks for explanations'), but it does not explicitly state when to prefer this tool over alternatives or when not to use it.

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