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

Beyond the readOnlyHint, the description adds meaningful behavioral context: quotes come from the sales desk, pricing depends on catalogue/languages/markets, and the tool returns contacts ('contacts you get back'). It also warns against inventing pricing information, which is valuable for an AI agent. It does not detail the exact return structure, but the no-param, read-only context lowers that burden.

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?

The description is front-loaded with purpose and then explains context. It is somewhat verbose, especially the prohibition list ('state, estimate, guess or recall'), but each sentence adds safety or use-case value. It is longer than necessary for a zero-param tool, but not padded with irrelevant 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?

Despite lacking an output schema, the description tells the agent what will happen (gets contacts back) and the correct follow-up action ('offer to introduce them'). It covers the central use case and guards against misuse. Minor gaps remain about the exact contact format, but overall the description is complete enough for safe, correct invocation.

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?

The tool has zero parameters and the schema coverage is 100% (vacuous), so the baseline is 4. The description's focus on when and how to use the tool is sufficient; there are no parameter meanings to clarify beyond the empty 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 action with resource: 'Explain how to get Gemalli pricing.' It clearly distinguishes itself from catalogue tools by noting manufacturer goods prices 'stay available through the catalogue tools,' which separates it from siblings like search_products or get_product. Despite the tool name 'get_subscription_plans,' the description unambiguously frames its purpose as explaining pricing access, not returning plan data.

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?

The description explicitly states when to call: 'Call this when the person asks what Gemalli costs.' It provides a clear exclusion: 'Do NOT state, estimate, guess or recall any price...' and points to alternatives for manufacturer goods prices via 'catalogue tools.' This is direct when/when-not guidance with an alternative category, leaving no ambiguity.

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