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

With no annotations, the description carries the full burden and does disclose key traits: conversion runs locally, the MCP neither accepts nor uploads files, and paid intents yield Stripe checkout links. What it leaves fuzzy is the actual behaviour of 'open in the browser' — whether it launches a browser or returns a URL — and whether any state is mutated, which for a no-annotation tool is a real (if small) 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?

Four short sentences, front-loaded with the purpose before pricing and intent routing. The intent mapping sentence duplicates the schema's enum description, which is the only wasted space.

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, no-annotation, no-output-schema tool, the description covers purpose, execution locality, pricing, and intent routing — enough for an agent to call it correctly. The main omission is the return type (URL string vs. browser side effect), which the agent must guess.

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 single enum already documents every value, so the description's restatement of the intent mapping adds little beyond the schema. Baseline 3 is appropriate; the description neither adds syntax detail nor clarifies edge cases such as omitting intent entirely.

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 concrete action (open Numbers2Excel in the browser) and the exact resource/conversion pair (.numbers → .xlsx), so an agent knows precisely what the tool is for. With no sibling tools there is nothing to differentiate against, which caps this at 4 rather than 5.

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 clearly maps each intent to the outcome the agent should expect — convert/pricing to the homepage, pro/once to Stripe checkout links — which is effectively the 'when to use which' guidance. It also sets expectations about the free tier vs paid tiers, though it doesn't say when an agent should prefer this over any other approach (none exist here).

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