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

Annotations already declare readOnlyHint=true, idempotentHint=true, openWorldHint=false and non-destructive, so the safety profile is covered. The description adds that costs are computed at 'the company's contracts' and invoices are 'checked against what Veqen expects', which is meaningful context about the data, but it says nothing about default behavior when month is omitted or how large the result set can be.

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?

A single dense sentence with no filler, and the most important scoping fact (month, with format) appears early. It is a verbless fragment, which slightly reduces readability but costs no tokens.

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 one-parameter read-only tool with an output schema and safety annotations, the description covers the returned content adequately without needing to restate return shape. The missing piece is optional-parameter behavior: with month defaulting to null and no required fields, an agent cannot tell what a bare call does.

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 parameter alone; it does convey the month semantics and its YYYY-MM format (though the schema pattern already enforces that). It fails to explain the null default — whether omitting month means the current month or all months — which is the one thing an agent actually needs beyond the 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 the resource (coding tools) and enumerates the specific fields returned per tool: connection status, cost at contract rates, plan, and invoice reconciliation against Veqen's expectations. That is far more specific than the tautological title, though it never explicitly contrasts itself with near siblings such as coding_agent_spend, reconciliation_status, or add_tool_invoice.

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?

There is no statement of when to reach for this tool versus alternatives like coding_agent_spend or reconciliation_status, and no exclusions. An agent must infer from the noun phrase that this is the per-tool monthly breakdown rather than the aggregate spend view.

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