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

Annotations cover the safety profile (non-read-only, non-destructive, non-idempotent, closed-world), and the description adds the critical trait that the credential is returned exactly once and cannot be read back. That is actionable behavior beyond the annotations, though it says nothing about failure or duplicate-instance behavior.

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 sentences, each carrying distinct information (what it does, the one-time credential, the personal-agent exclusion), with the core action front-loaded. Slightly dense but no wasted sentences.

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 no output schema, the description correctly fills the gap by explaining the returned credential and its one-time visibility, plus the scope limitation. It leaves minor gaps around error cases and whether repeated calls create duplicate instances, but covers what an agent needs to invoke 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 is 100%, so name, metadata, and agent_slug are already documented in the schema. The description confirms the agent_slug source but adds no syntax or format guidance beyond what the schema provides; 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 ("Register an instance of a service agent and mint its credential") and scopes it to a runtime the CLI cannot install, distinguishing it from create_agent and update_agent_instance. An agent can identify the operation without opening the schema.

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?

Gives a clear usage condition ("for a runtime the withhuman CLI does not install") and an explicit exclusion: personal agents' instances belong to the member who enrolls them through the CLI. It routes the agent away from misuse, though it does not name a sibling tool as the alternative.

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