set_credential

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

With no annotations, the description fully discloses behavior: it writes to a specific file (~/.local/state/external-agents/keys.env) with permissions (mode 0600) and persists across sessions. It also explains the impact on dispatch. This is comprehensive.

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?

A single sentence that front-loads the purpose ('Persist an API-key env variable') and includes specific details (file path, permissions, effect on dispatch) without any redundant information.

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 credential-setting tool with 2 required parameters and no output schema, the description covers all essential aspects: what it does, where it writes, persistence behavior, and impact on dispatch. No gaps remain.

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?

The description adds meaning beyond the schema by stating the tool deals with API-key env variables, implying env_name is the variable name and value is the key value. Though schema coverage is 0%, the description provides enough context to infer parameter roles.

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 the tool persists an API-key environment variable for future sessions, specifying the verb 'persist', the resource 'API-key env variable', and the effect on dispatch and future sessions. It also includes the file path and permissions, making the purpose unambiguous.

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 implies usage for setting persistent environment variables that affect dispatch and future sessions. While it does not explicitly state alternatives or when not to use, the sibling tools are unrelated, so no confusion arises. A clear when-to-use context is provided.

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