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

Aligns with annotations (readOnlyHint, idempotentHint, destructiveHint) and adds useful behavioral context: live balance, faster, no credential exposure. No contradictions.

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 sentences, each purposeful: first states purpose with resource specificity, second provides usage guidance. No wasted words, front-loaded.

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?

Complete for its purpose: explains what it does, when to use, and key benefits. Output schema exists but not shown; description covers all needed context for an agent.

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?

Single parameter card_id with basic schema description 'The card ID'. Description adds 'of ONE virtual card' but doesn't elaborate on format or constraints. Schema coverage is 100%, so baseline 3 is appropriate.

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 clearly states the tool returns the live balance of a single virtual card, distinguishing it from get_balance (overall cash balance) and get_card_details (which exposes sensitive credentials).

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 advises preferring this tool over get_card_details when only verifying available funds, citing speed and credential safety. Also contrasts with get_balance.

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