fetch_by_time

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

With no annotations, the description alone must convey behavior. It does disclose the key behavioral nuance that offsets are resolved to the first position at or after the timestamp. But it does not state how this behaves when partition_id is -1, what happens when no offset exists at/after the timestamp, or how max_results bounds the result.

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?

One sentence, verb-first, with no filler or repeated schema content. The essential semantic is front-loaded and the sentence earns its place.

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 description is adequate for a simple fetch tool because required parameters and timestamp semantics are covered by the schema plus the one-line description, and an output schema exists so return values need not be spelled out. However, the lack of sibling differentiation, edge-case behavior, and any behavioral context beyond the core fetch rule leaves it incomplete for agents choosing among the six sibling tools.

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 75%, so the baseline is near 3. The description adds real meaning beyond the schema by explaining that timestamp_ms controls offset selection rather than exact-time filtering; the schema only says 'Unix epoch time in milliseconds.' It does not clarify max_results, but that parameter has a concrete default and bounds in the schema.

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 names a specific operation ('Fetch messages') and a precise selection rule ('first offset at or after a timestamp'), which distinguishes it from fetch_latest, fetch_by_offset, and search_messages without needing the schema. It is not a tautology and identifies the resource as timestamp-anchored Kafka messages.

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 intended use case is implied: call this when messages starting from a given point in time are needed. However, there is no explicit statement of when to prefer fetch_by_time over fetch_by_offset, fetch_latest, or search_messages, and no exclusions or prerequisites.

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