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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered by structured data. The description adds real value beyond that — result ordering and the fields returned (tags, digest, push date, size) — but says nothing about pagination, whether maxResults truncates silently, or what happens when the repository is empty or missing.

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 with the core behavior front-loaded and no filler. The example sentence is somewhat redundant with the repositoryName schema description (which uses the same 'your-tenant-storefront' sample) but it does clarify intent cheaply.

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 with an output schema and full schema coverage, the description covers what it does, how results are ordered, and what fields come back. The remaining gap — truncation behavior at maxResults and error cases for nonexistent repositories — is minor but not fully negligible.

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%, so region, profile, context_id, maxResults and repositoryName are all documented in the schema itself. The description only restates the repositoryName example and the sort order, adding no meaning to maxResults truncation semantics or region/profile precedence — 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 images in an ECR repository') plus the ordering ('sorted by date, most recent first'), which is enough to distinguish it from aws_ecr_repos (which lists repositories rather than images). It never names that sibling explicitly, so the differentiation is inferred from the resource noun 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?

Usage is implied by the required repositoryName parameter and the imagery of the example, but there is no explicit 'use this when...' guidance, no exclusions, and no mention of when to prefer aws_ecr_repos or another image-inspection path. An agent can infer the context but must do the routing work itself.

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