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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds genuinely new behavior: a PREMIUM license gate, per-row mapping rules (dated deadlines become VEVENTs with citation in description plus a VALARM; open-ended rows go to CSV only), and a documented error contract (returns {"error": ...} rather than a protocol error, safe to retry). That is well beyond what the structured fields convey.

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?

Front-loaded with purpose, then example input/output, then usage and error behavior – a sensible order with no filler sentences. The inline JSON snippets make it longer than strictly necessary, but each carries real information.

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 4-parameter export tool with full schema coverage, an output schema, and explicit annotations, the description still covers the license constraint, input provenance, output shape, and failure/retry behavior. An agent has everything needed to call it correctly and recover from bad input.

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 100%, so baseline would be 3, but the description adds meaning the schema does not: what the deadlines rows actually contain and how they are split between VEVENTs and CSV, plus a concrete example input object. The alarm and incident_ref semantics largely duplicate schema text, keeping it below a 5.

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 and resource ('Export computed deadlines as an iCalendar file and CSV rows') and explicitly separates itself from compute_deadlines ('Not for computing deadlines'). An agent can distinguish it from all siblings including compute_deadlines_multi without opening a schema.

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 the positive trigger ('Use when the timeline needs to land in a calendar or a ticket'), the negative case ('Not for computing deadlines'), and the upstream source of input (rows from compute_deadlines / compute_deadlines_multi). Nothing about when to select this tool is left to inference.

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