Adding capability made the agent less capable
monday.com hit this building Sidekick, and rebuilt the system around what they found. https://www.langchain.com/blog/building-monday-com-sidekick-why-capable-agents-need-more-than-just-tools
The cause was not the tools themselves.
It was their descriptions.
Overlapping descriptions made the choice ambiguous, and the model burned tokens deliberating between near-identical options.
Every tool you register is text in the context window, competing with every other tool for the model's attention.
Most teams treat the tool list as a feature list, where more is self-evidently better.
A tool list is a context problem wearing a capability costume.
The rebuild replaced the pile with seven layers: • product context • context and permission layer • orchestration agent • subagents • tools • sandboxes • observability and evaluation
The layer worth stealing is the second one.
monday.com treats permission-aware retrieval as infrastructure rather than as a filter applied to results after the fact.
That ordering matters, because an agent that retrieves first and filters second has already pulled data it was never allowed to see into its own context.
A permission check that sits outside the retrieval path is decoration.
The remaining layers are how a growing agent avoids collapsing under its own surface area.
Subagents run narrower objectives on smaller toolsets, which bounds the number of tools any single model has to choose between. Sandboxes assume something will go wrong. Observability tells you when it did.
A demo agent looks better every time you hand it another tool. A production agent gets better every time you take one away.
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