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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the safety profile is fully covered. The description adds content-level context (what the deal record contains), but says nothing about auth requirements, rate limits, or behavior on an unknown slug — modest added value over the annotations.

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?

A single sentence that front-loads the resource and scope, with the sibling reference placed inline. No filler; every clause (slug source, return contents) earns its place.

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?

There is no output schema, so the description correctly compensates by naming the returned fields (offer, eligibility, expiry, claim instructions). It only omits edge-case behavior such as what is returned for a missing or expired slug, which keeps it just short of fully complete.

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 schema already gives slug examples ('notion', 'aws-activate'), so the baseline is 3. The description goes beyond it by indicating the slug's provenance ('from search_deals'), which tells the agent where the identifier must come from — genuine semantic value for the only parameter.

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?

States a specific verb+resource ('Full details for one SaaSOffers deal by slug') and enumerates the payload (offer, eligibility, expiry, claim method). It is clearly distinguishable from search_deals and list_categories, which return collections rather than a single deal.

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 parenthetical '(from search_deals)' tells the agent the precondition — first find a slug via search_deals, then call this tool. No explicit exclusions or when-not conditions are given, but the calling context is unambiguous for a 1-param lookup tool.

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