set_config

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

With no annotations, the description carries the full behavioral burden and discloses the return value, failure behavior with available choices, and the side effect of reopening an idle session. It does not discuss permissions, reversibility, or persistence, so it is strong but not complete.

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 three tight sentences, front-loaded with the core action. Each sentence adds useful information: return value, validation failure, and idle-session reopening.

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?

Given an output schema and no annotations, the description covers the key mutation behavior, error handling, and reopening behavior. The remaining gap is fuller parameter semantics for config_id and value.

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 coverage is only 33%, so the description must compensate. It helps by naming example config ids and explaining that unknown ids or values fail with available choices, but it still leaves config_id and value formats somewhat implicit.

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 uses a specific verb, "Change," and a specific resource, "session config option," with examples like model, reasoning_effort, and mode. It is clearly distinct from sibling session lifecycle tools, though it does not explicitly route against any alternative.

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 when to use it: changing a session configuration option. It also explains error behavior and idle-session reopening, but gives no explicit when-not guidance or alternative comparison.

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