docker-facts

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 adds meaningful behavioral detail beyond annotations: it explains hit results (size, platforms, arm64/amd64 support, digest), miss results (image exists but tag wrong; real tags listed newest first), and the default-to-latest behavior. This gives the agent a model of the tool's behavior in both outcomes.

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 description is compact and front-loaded: a clarifying question, a single use-case sentence, then conditional hit/miss behavior and the default rule. Every sentence earns its place, and there is no filler or redundant repetition of schema fields.

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 read-only lookup tool with a rich output schema and strong annotations, the description is complete. It covers the intended use case, the default parameter, both hit and miss outcomes, and the self-correction capability. There are no critical gaps an agent would need to guess about.

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 the parameter burden is already carried by the schema. The tool description adds the default-to-latest behavior and the 'before writing a FROM line' context, but the schema already explains the name format and tag examples. The description does not meaningfully extend the parameter semantics beyond what the schema provides.

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 opens with a specific, answerable question: 'Does this image:tag exist, how big is it, and which platforms does it cover?' This clearly states the verb, resource, and scope. It also differentiates itself from sibling tools by describing miss behavior that returns real tags so the caller can correct the tag, which is a distinct capability beyond generic image info or tag listing.

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 description gives explicit guidance: 'Use this before writing a FROM line or a compose file.' This clearly tells the agent when to invoke the tool. It doesn't explicitly name alternatives or state when not to use it, but the hit/miss behavior and correction capability give enough contextual grounding to select it appropriately.

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

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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the operation is clearly safe. The description adds useful non-obvious context: 'Archived images still pull but receive no security patches.' No contradiction with 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?

The description is compact, front-loaded with the core facts, and each sentence adds value. There is no wasted text or redundant restating of the title.

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 one-parameter, read-only tool with an output schema and strong annotations, the description covers purpose, use case, and maintenance implication. Nothing important is missing for an agent to call it correctly.

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 for the single required parameter is 100%, so the schema fully documents the 'name' format. The description does not add extra parameter detail, but the baseline of 3 is appropriate when the schema carries the burden.

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 clearly states what the tool returns: repository facts such as official status, pulls, stars, and archived state. It is easy to understand the tool's purpose, though the description does not explicitly contrast it with the sibling tag-related tools.

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 description gives clear usage intent: 'Use to judge whether an image is the canonical one and still maintained.' It does not mention exclusions or alternatives, but the context is sufficient for a simple read-only metadata tool.

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

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds genuinely useful behavioral context beyond those: the result ordering ('most recently updated first') and the fact that each entry includes size and platform list.

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?

Two sentences with no wasted content. The first sentence names the resource and ordering; the second provides selection guidance and payload context. Every sentence 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?

With full param documentation, clear annotations, and an output schema present, the description covers the key behavioral traits (sort order, payload contents) and selection context. Nothing essential is missing for an agent to invoke this tool correctly.

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 the schema already documents 'name' and 'limit' clearly. The tool description adds no additional parameter-specific meaning, so baseline 3 is appropriate.

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 states a specific verb and resource: 'Real tags for an image, most recently updated first.' It also differentiates the tool from a verification-oriented sibling by framing it as 'choosing a tag rather than verifying one.'

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 description explicitly says when to use the tool ('Use when choosing a tag'), when not to use it ('rather than verifying one'), and explains the practical benefit: each entry carries size and platform list, so a choice can be made without a second call.

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