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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description still adds real value by spelling out the absence of side effects ('does not create an account, save anything or send any message') and by describing the human-in-the-loop follow-up, which annotations cannot 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 action and its result are front-loaded in the first clause, with the non-side-effect disclaimer following. It is compact with no filler, though the single long opening sentence packs three ideas together rather than separating them.

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?

An output schema exists, so return values need not be described, and the description sensibly fills the gap an agent would otherwise have about the signup-link flow. Nothing critical is missing, though the relationship to sibling lookup tools is left unstated.

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 100% — city, move_in and budget_max_eur are all documented with valid slug/name formats and constraints in the schema itself. The description adds no parameter-level detail (e.g. how budget_max_eur or move_in affect the returned link), so the 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?

The description gives a specific verb and resource: 'Check that a city is supported and return the Socials Homes signup link for it.' It also corrects the potentially misleading name by clarifying that no account/search is actually created, which is strong disambiguation, though it never names the sibling tools (check_city_supply, list_cities) it could be confused with.

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?

Usage is implied rather than stated: it explains what the tool returns and what happens next, so an agent can infer this is the entry point after picking a city from list_cities. However, it never says when to use this versus check_city_supply or get_plans, and gives no exclusion conditions.

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