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

Annotations already declare readOnlyHint=true, so the safety profile is covered; the description adds the underlying API endpoint (GET /v1/apps/{app}/addons) and the response envelope ({ addons: [...] }), which is meaningful since no output schema exists. Pagination or result-size behavior is not disclosed, keeping it short of a 5.

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?

Three short sentences, zero filler, with the core purpose front-loaded before the API and return-shape details. Every sentence carries information an agent can use.

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 simple read-only list tool the description covers purpose, scope, endpoint and return envelope, which is sufficient given annotations and full schema coverage. Only pagination/ordering behavior is absent.

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?

Single 'app' parameter with 100% schema description coverage that already explains name-or-id forms. The description adds no parameter-level semantics beyond what the schema provides, 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?

States a specific verb and resource ('List the addons') plus a parenthetical scoping clarification ('databases, services') and 'provisioned on an app', which separates it from the sibling scalingo_list_addon_providers (available providers vs. actually provisioned addons). No ambiguity about what is returned.

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 by the resource scope (needs an app and lists its addons), but there is no explicit guidance on when to prefer this over scalingo_request or scalingo_list_addon_providers. Nothing is misleading, but the agent must infer the selection.

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