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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered; the description adds genuine value by disclosing what the response contains — one pick per slot plus alternatives, the tightest published LLM requests per day, card/program warnings, and a shareable URL. That output disclosure is important since no output schema exists.

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 dense but front-loaded passage with no filler; the template/slot model comes first and the optional modifiers last. It is slightly crammed — several distinct ideas in one sentence — but every clause carries 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 no output schema, the description correctly carries the return-value burden and explains the nested `picks` object's purpose. What remains thin is guidance on failure modes (invalid template, unknown offer slug) — a minor gap for a read-only builder.

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 description coverage is 75%, so the schema already documents picks, noCard, and region. The description reinforces the semantics ('one free pick per slot', 'pin a slot to an offer slug', 'limit to a country') but adds no format or edge-case detail beyond the schema, so baseline 3 applies.

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 and resource ('the aifree.dev/stack builder') and enumerates the templates (chat, rag, image, voice, agent, finetune) and slots it composes, so an agent knows this produces a full stack rather than a single lookup. It does not explicitly name a sibling (e.g. compare_offers or search_free_ai_offers) to contrast against, so differentiation is implied by the 'builder' framing rather than stated.

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 optional modifiers (pin a slot, require no card, limit to a country) hint at when to reach for this tool, but they describe parameter usage rather than selection criteria. There is no explicit statement of when to choose build_stack over compare_offers or search_free_ai_offers, leaving the routing to inference.

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