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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered; the description adds genuinely non-structured context: UTC day boundaries, aggregation across all keys, exclusion of MCP handshakes, the required 'requests:read' scope with its default/per-key behavior, and that the call is free. It doesn't describe return shape, but with no output schema and a read-only profile that is a minor gap.

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 dense sentences, front-loaded with the core behavior, then the alternative, then the permission prerequisite. Every clause earns its place (scope qualifiers, permission name, console path), though the permission sentence is somewhat long for a secondary detail.

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 single-parameter, read-only, non-destructive tool with no output schema, the description covers scope, time semantics, aggregation, exclusions, permission requirements, cost, and the sibling alternative for spend. Nothing an agent needs to call it correctly is missing.

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 coverage is 100% and the 'days' property already documents 'Number of days, default 7'. The description's 'UTC days' adds a small semantic clarification about how days are counted, which the schema does not state, but nothing about the 1–90 range or default beyond what the schema carries. Baseline 3 with a marginal add.

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 precise verb+resource ('Calls per day for the last N days') and qualifies the scope with 'UTC days, all keys combined, MCP handshakes excluded'. It also names the sibling to use for a different concern ('For spend use everyinfra_billing'), so an agent can distinguish it from everyinfra_requests and everyinfra_billing without opening schemas.

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?

Explicitly routes spend-related queries to everyinfra_billing and gives concrete prerequisites for use (the 'requests:read' permission, with defaults and console steps). It lacks an explicit statement of when this tool is the wrong choice beyond the spend case, so it falls short of a full when/when-not treatment.

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