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

Beyond the annotations (readOnlyHint, idempotentHint), the description adds critical behavioral details: the 24-hour lifetime, failure on unknown ID, and the instruction to treat failures as permanent rather than transient. It also clarifies that no API key or account is required. These details are not captured by annotations and significantly improve the agent's ability to handle errors correctly.

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 well-structured and front-loaded with the primary purpose. It is composed of three sentences that flow logically: purpose, failure behavior, and authentication. It avoids redundancy with annotations and schema. While it is slightly verbose with the sha256_hash detail (which may not be essential for calling the tool), it remains clear and efficient overall.

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?

The tool is simple (one parameter, output schema exists), and the description covers all essential aspects: what it does, how to interpret failures, and that no auth is needed. Combined with annotations that already declare readOnly and idempotent, an agent has everything required to call it correctly and handle responses appropriately. No critical information is missing.

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 input schema already provides a description for storage_id ('The UUID that store_temporary_data returned.'), and the schema coverage is 100%. The tool description adds little about the parameter itself beyond restating its origin; the mention of sha256_hash appears to relate to the output or validation but is not directly tied to the input parameter. Since the schema fully documents the parameter, the baseline of 3 is appropriate.

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's purpose: 'Fetch back a JSON value that store_temporary_data saved earlier' and 'Returns the value exactly as it was stored.' It specifies the resource (JSON value) and the verb (fetch back), and it distinguishes itself from the sibling store_temporary_data by explicitly referencing it. The failure semantics are also clearly outlined, which further clarifies the tool's role.

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: it should be used to retrieve a value previously saved via store_temporary_data. It provides concrete guidance on how to interpret failures ('treat a failure as expired or never written rather than as a temporary fault worth retrying'), which is valuable operational context. It does not explicitly list alternative tools or when not to use it, but the direct counterpart reference makes the use case clear enough for an agent.

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