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

Annotations already establish readOnlyHint and idempotentHint, so safety is covered; the description goes further by disclosing what the returned connection card contains (auto-fill state and expiration time), which is valuable since there is no output schema. It does not describe behavior for an unknown/expired session id, a minor gap.

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 front-loaded sentence with no filler; the verb and the returned fields are packed in without repetition.

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 one-parameter read with no output schema, the description conveys the key return fields (auto-fill flag, expiry) and the id source is in the schema. It stops short of enumerating the rest of the connection card or error conditions, but is solidly 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?

There is one parameter with 100% schema description coverage, and the schema already states the id comes from sandbox_create_session. The description's 'by id' adds no meaning beyond the schema, so the baseline 3 applies.

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 gives a specific verb ('Re-fetch') and resource ('a sandbox session's connection card') qualified by id, so the agent knows exactly what is retrieved. It does not explicitly contrast with siblings such as sandbox_get_status or sandbox_create_session, but 'Re-fetch' implicitly signals it operates on an already-created session.

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 word 'Re-fetch' implies the tool is for refreshing an existing session rather than creating one, but the description never states when to use this versus sandbox_get_status, sandbox_get_messages, or the fixsim_get_session sibling. Usage is inferable but not spelled out.

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