context_save

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

With no annotations, the description carries the burden and does well: it warns that an existing key is overwritten, explains ttl_seconds semantics (0 = never), and states per-identity scoping and storage backend. It doesn't mention return format or error cases, but the key behavioral traits are disclosed.

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 dense with useful information: purpose, overwrite behavior, expiry, scoping, and storage backend. No filler or redundant restatement of the schema.

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 no annotations, no output schema, and 4 parameters, the description covers the essential context: what state is saved, where it's stored, how it expires, and scoping. It omits return values and failure modes, but for a straightforward 'save' operation this is adequate.

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%, so the description must add meaning. It clarifies ttl_seconds ('optionally expiring... 0 = never'), app_id ('Per-identity — scoped to your app_id'), and key ('under `key`'). The value parameter is implied as the state being saved but isn't explicitly described, so not a 5.

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 verb and resource: 'Save ephemeral working state under `key`'. It clearly distinguishes this from sibling store_* tools by emphasizing 'ephemeral' working state, per-identity scoping, and SOIL storage, making the tool's niche clear.

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?

It provides practical usage context: use for ephemeral state, see ttl_seconds for expiry, and note that no Postgres is needed. It doesn't explicitly name alternatives or exclusions, but the 'ephemeral' and storage distinctions effectively guide when to choose this tool.

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