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

Annotations only say readOnly=false, destructive=true, idempotent=false; the description adds genuinely new behavior: the server assigns the 'Cycle N' number per project, absent fields are left untouched while `name: null` clears, cycles in the same project may overlap in time, and the create response reports the resulting `workspace`. That is exactly the context annotations cannot express.

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 the create-vs-update rule, then per-field semantics, then sibling routing — a sound information order with no filler. It is dense (heavy semicolons and parentheses) and could be split into shorter sentences for scanability, but no sentence is expendable.

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 5-param mutation tool with no output schema and no annotation detail, the description covers write semantics, field-omission behavior, server-side numbering, temporal constraints, and the shape of the create response (`workspace`). An agent has everything needed to call it correctly on first attempt.

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 0%, so the description carries full burden — and it does: `startsAt`/`endsAt` are epoch ms with endsAt after startsAt, `projectId` is required on create but ignored on update, `name` is optional and null clears it. Notably it supplies create-time requirements that the schema's empty `required` list omits.

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?

Opens with a specific verb+resource pairing ('Crea un cycle (sprint)... o actualiza uno existente') and immediately disambiguates the two modes by the presence of `id`. The parenthetical '(sprint)' plus the project scoping makes it distinguishable from save_issue and save_project without reading any 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?

Explicitly routes the agent to siblings: 'Para meterle issues, usa save_issue con cycleId' and 'Usa list_projects/list_cycles para los ids'. It also states the mode-selection rule (no id = create, id = update) and the invariant 'Un cycle NO se mueve de proyecto', so the caller knows what this tool will not do.

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