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

Annotations cover the safety profile (not read-only, not idempotent, open-world), so the bar is lower, but the description adds genuinely useful behavior: it returns production AND test API keys on success, and paid tools require a separate subscription. It does not say whether the code is single-use or what happens on failure.

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?

Purpose is front-loaded in the first line, precedence follows, and the example is compact. Slightly more prose than strictly necessary (the subscription line could be tightened), but every sentence carries usable information.

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?

With an output schema present and full param coverage, the description needn't explain return values, and it still adds the key behavioral facts (returned keys, subscription gate, prerequisite call). Complete enough for an agent to invoke correctly, missing only failure/retry behavior.

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% with both parameters documented, so the schema does the heavy lifting (code = '6-digit verification code from that email'). The description adds only the worked example showing the call shape/order and no format nuances 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 states a specific verb+resource ('Verify your email and receive your API key') and ties it to a clearly named sibling flow (mcp_register), so an agent can distinguish it from the many lookup-style siblings. Scope and outcome (production and test API keys) are explicit.

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 states the precondition and sequencing explicitly: 'After calling mcp_register, check your email for the 6-digit code and pass it here.' It also adds a separate activation condition (ohmyfin.ai/subscription) for paid tools, so the agent knows when the tool is sufficient and when extra action is needed.

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