postfix_log_trend

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

Annotations already declare readOnlyHint=true, openWorldHint=false, and idempotentHint=false, so the safety profile is covered. The description adds useful context about what is computed (buckets, direction semantics) but discloses no operational traits such as cost, rate limits, or behavior on missing data. A 3 is appropriate with annotations carrying the safety burden.

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?

Two dense sentences, front-loaded with the core output shape before the usage hint. Every clause carries information, though the direction-value enumeration makes it slightly heavier than strictly necessary.

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 read-only analytics tool with 100% schema coverage and an output schema, the description covers purpose, output content, and the direction interpretation well. It is complete enough to invoke correctly, with only marginal room for clarifying edge behavior.

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 100%, with all four optional params (top, since, bucket, domain) documented in the schema itself. The description alludes to windows and buckets but adds no format or default detail beyond the schema. Baseline 3 is correct when the schema does the heavy lifting.

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?

States a specific verb+resource: computes per-destination deferral rate over time buckets from the mail log, returning sent/deferred counts, rate, and a direction verdict. This clearly separates it from siblings like postfix_log_stats or postfix_queue_summary, though it doesn't name those siblings explicitly.

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?

Gives a clear usage context: 'Use to see whether Gmail/Outlook/etc. is getting better or worse.' That is a concrete when-to-use scenario. It stops short of naming alternatives (e.g. postfix_log_stats) or stating exclusions, so it lands at 4 rather than 5.

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