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

Annotations already declare read-only, open-world, idempotent, and non-destructive behavior. The description adds useful context beyond that: no key or account is needed, each row includes item, monthly cost, and acquisition method, and some items are purchased via chat, some via dashboard setup, some via conversation. This meaningfully enriches what annotations alone convey.

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 longer than average and uses emphatic capitalization, but every sentence carries distinct information: scope, usage triggers, sibling differentiation, row contents, acquisition methods, and authentication needs. It is somewhat repetitive in warning against market_search, but the repetition reinforces a critical failure mode.

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 parameterless read-only catalog tool with no output schema, the description is remarkably complete. It explains what the output rows contain, how items are obtained, that no credentials are needed, and how this tool differs from the market-oriented siblings. An agent has everything needed to select and invoke it correctly.

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 describes this fully, so the baseline is 4. The description confirms the tool is a catalog listing rather than a parameterized query, and explains what each returned row contains, which is sufficient for a no-argument tool.

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 this tool returns the platform's own add-ons and subscription lines, not marketplace goods. It explicitly differentiates itself from market_walk and market_search, so an agent can immediately identify the correct resource.

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 gives explicit when-to-use triggers ('asks what the platform offers, what it costs, what plans or add-ons exist') and explicit when-not-to-use guidance, naming market_walk/market_search as the alternatives. It even warns that searching the market for 'saas' will correctly find nothing and that this absence is not evidence that the offer doesn't exist.

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