system_login

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

Discloses a significant security trait (password sent as tool argument, likely logged) and implies statefulness by mentioning that system_logout clears credentials. Annotations only provide readOnlyHint=false and destructiveHint=false, so this added context about logging and credential lifecycle goes beyond the schema. However, it does not explicitly state whether the tool persists credentials to ~/.docker/config.json, leaving a minor ambiguity.

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 front-loaded with the purpose sentence, followed by a crucial security warning, then an args list and return format. Every section earns its place, though the args block duplicates parameter names already in the schema; however, the added explanations justify the length. Not overly verbose.

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 tool with 6 parameters and no output schema, the description is quite complete: it covers return format, security implications, related tools, and parameter semantics. It does not mention error conditions or prerequisites like Docker being running, but these are less critical for a login operation and may be assumed.

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 0%, yet the description's args list provides meaningful one-line explanations for all 6 parameters, including defaults (registry defaults to Docker Hub) and behavior (reauth forces re-authentication). This fully compensates for the absence of schema descriptions and adds value beyond parameter names.

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?

Description begins with 'Authenticate with a Docker registry', a specific verb+resource statement that clearly distinguishes this from other system tools like system_logout. It further clarifies purpose by noting credentials enable image_pull/image_push and that system_logout clears them.

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?

Explicitly advises preferring `docker login` on the host and avoiding agent loops due to credential logging risk. It also states when credentials are needed (private repositories) and names the alternative for clearing credentials (system_logout), providing clear when/when-not guidance.

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