Retrieves a stored context using its key, returning an error if the key is missing or has expired, and purges expired entries.
Read a saved context by key. Returns {error: not_found} if absent, or {error: expired} (and purges it) if its TTL has passed.
| Name | Required | Description | Default |
|---|---|---|---|
| key | Yes | ||
| app_id | Yes |
Changes observed during successful MCP inspections.
v2.2.3Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
The description discloses a surprising side effect: it purges expired entries when returning an expired error. This goes beyond the annotations, which only say readOnlyHint=false and destructiveHint=false. It also specifies the exact error shapes, making behavior predictable.
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 compact and front-loaded: the primary purpose is in the first sentence, and the error behaviors follow in a single second line. No filler or redundancy.
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 2-parameter tool with no output schema, it covers the core action and error cases. However, it omits any explanation of what app_id is for and doesn't mention any constraints (e.g., key uniqueness, TTL semantics beyond the expired purge). Given the spare schema, more detail would help an agent use 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 coverage is 0% and the description provides no extra meaning for 'key' or 'app_id'. It doesn't clarify the relationship between the two or the expected formats. The description alone does not compensate for the missing schema descriptions, leaving the agent to guess at the 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 states a specific verb ('Read') and resource ('a saved context by key'), and the error behaviors make the purpose unambiguous. It distinguishes itself from siblings like context_save, context_list, and context_expire by focusing on retrieval of a single keyed value.
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 clearly implies usage for reading a specific context, but it does not explicitly contrast with context_list (list all) or context_expire (force expiry). No alternatives are named or excluded, so the agent must infer when to choose this over siblings.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.